Terms A–Z

51% Attack

Also: majority attack

When a single miner or coalition controls most of a proof-of-work network's hash power and can reorder or censor transactions.

Access Control List (ACL)

A list of permissions attached to a resource that specifies which users or systems may access it and what actions they can perform.

Account Abstraction

Also: ERC-4337

Wallet features letting smart contracts pay gas, batch actions, and define custom auth rules, e.g. ERC-4337.

Active Directory Security

Practices and controls for protecting Microsoft Active Directory, including securing domain controllers, privileged groups, Kerberos, and detecting identity abuse.

Address Poisoning

Sending look-alike addresses' micro-transactions so users copy the wrong recipient from history.

Advanced Encryption Standard (AES)

A widely adopted symmetric encryption standard used to protect data at rest and in transit with 128, 192, or 256-bit keys.

Advanced Persistent Threat (APT)

Also: APT

A prolonged, targeted attack campaign in which an adversary gains access to a network and remains undetected for an extended period, often exfiltrating data or maintaining influence.

Adware

Software that displays unwanted advertisements, often bundled with free programs and sometimes used as a delivery mechanism for other threats.

Agentic AI

Also: AI agents

AI systems that plan, use tools, and take multi-step actions toward a goal with limited human intervention at each step.

AI Red Teaming

Structured testing of AI systems to uncover harmful outputs, jailbreaks, data leakage, and misuse before deployment.

Air Gap

A security measure that physically or logically isolates a system from unsecured networks, preventing remote access entirely.

Airdrop

Distribution of free tokens to wallets for promotion, loyalty, or governance participation.

Algorithmic Stablecoin

Stablecoin peg maintained by protocol rules and incentives rather than full fiat backing.

Altcoin

Also: alternative coin

Any cryptocurrency other than Bitcoin.

AML (Anti-Money Laundering)

Also: crypto AML

Controls requiring crypto businesses to monitor and report suspicious financial activity.

AMM (Automated Market Maker)

DeFi pricing via liquidity pools and formulas instead of centralized order books.

Anomaly Detection

Identifying activity that deviates from established baselines, often using statistics or machine learning to flag potential intrusions.

Antivirus

Software that detects, quarantines, or removes known malware using signatures, heuristics, and behavioral analysis.

API Gateway

A front door for APIs that handles routing, authentication, rate limiting, and observability between clients and backend services.

API Security

Protecting application programming interfaces through authentication, authorization, input validation, rate limiting, and secure design.

Approval Phishing

Tricking users into signing token approvals that let attackers drain wallets.

Arbitrage (Crypto)

Exploiting price differences across exchanges, pairs, or chains for profit.

ARP Poisoning

Also: ARP spoofing

An attack that manipulates ARP tables on a local network to intercept or redirect traffic, enabling eavesdropping or MitM attacks.

ASIC Mining

Mining with hardware designed for one hash algorithm, dominant on Bitcoin.

Asset Inventory

A maintained catalog of hardware, software, cloud resources, and data that supports vulnerability management, patching, and incident response.

Asymmetric Encryption

Encryption using a public-private key pair; the public key encrypts data and the private key decrypts it, enabling secure key exchange and digital signatures.

Atomic Swap

Also: HTLC swap

Trust-minimized cross-chain trades using hash time-locked contracts.

Attack Surface

The sum of all points where an unauthorized user could enter or extract data from an environment — including software, hardware, users, and configurations.

Attack Tree

A diagram that maps goals and steps an adversary might take to compromise a system, used in threat modeling to prioritize defenses.

Attack Vector

The path or method an adversary uses to gain access or cause harm, such as email, web apps, USB devices, or stolen credentials.

Audit Log

A tamper-evident record of security-relevant events such as logins, configuration changes, and access to sensitive data.

Authentication

Also: AuthN

The process of verifying that someone or something is who or what they claim to be, typically before granting access to a system or resource.

Authentication Bypass

Exploiting flaws to gain access without valid credentials, often through logic bugs, default passwords, or session manipulation.

Authorization

Also: AuthZ

The process of determining which resources an authenticated identity is allowed to access and what actions they may perform.

Beacon Chain

Ethereum proof-of-stake coordination chain merged with the execution layer at The Merge.

BEP-20

Token standard on BNB Smart Chain, analogous to ERC-20 on Ethereum.

BGP Hijacking

Illegitimate announcement of IP prefixes via BGP routing, redirecting traffic through attacker-controlled networks for surveillance or disruption.

Binary Exploitation

Techniques that abuse memory corruption or logic flaws in compiled programs to execute arbitrary code or escalate privileges.

Birthday Attack

A cryptographic attack that exploits hash collisions, relevant when hash output size is too small for the security required.

Bitcoin

Also: BTC

The first decentralized cryptocurrency, using proof of work and a fixed supply cap of 21 million coins.

Bitcoin Ordinals

Also: Ordinals

Numbering satoshis to inscribe data on Bitcoin, enabling NFT-like assets on the base chain.

Black Hat

A hacker who violates laws or ethics to break into systems for personal gain, sabotage, or unauthorized access.

Blob Transaction

Also: EIP-4844 blob

Ethereum transaction carrying ephemeral data blobs for cheaper Layer 2 posting under EIP-4844.

Block

A batch of validated transactions and metadata linked to the previous block, forming the chain in a blockchain ledger.

Block Cipher

A cipher that encrypts fixed-size blocks of data, commonly used in modes such as CBC or GCM with AES.

Block Explorer

A web tool to browse blocks, transactions, addresses, and contract activity on a blockchain.

Block Hash

Cryptographic fingerprint of a block header used to link blocks in the chain.

Block Header

Metadata summarizing a block: parent hash, timestamp, roots, nonce, and consensus fields.

Block Height

The number of blocks since the genesis block, used to measure chain progress.

Block Propagation

How new blocks spread across nodes; delays can advantage miners in competing chains.

Block Reward

Newly minted coins plus fees paid to the miner or validator that creates a block.

Block Time

Target average interval between consecutive blocks on a network.

Blockchain

Also: distributed ledger technology

A distributed ledger of cryptographically linked records maintained by a network without a single central authority.

Blue Team

Defensive security personnel who monitor, detect, and respond to threats and improve organizational security posture.

Botnet

A network of compromised devices controlled remotely, often used for DDoS, spam, credential theft, or cryptocurrency mining.

BRC-20

Fungible token standard on Bitcoin implemented via ordinal inscriptions and off-chain indexers.

Bridge (Cross-Chain)

Also: blockchain bridge

Infrastructure that locks or burns assets on one chain and mints or releases equivalent value on another, enabling cross-chain transfers.

Bridge Exploit

Also: bridge hack

Attack on cross-chain bridge code or keys that drains locked or wrapped assets.

Bring Your Own Device (BYOD)

A policy allowing personal devices on corporate networks, requiring extra controls for enrollment, isolation, and data protection.

Brute Force Attack

A trial-and-error method used to guess passwords, encryption keys, or other secrets by systematically trying many possible combinations.

Buffer Overflow

A flaw where input exceeds allocated memory, potentially overwriting adjacent data and enabling arbitrary code execution.

Bug Bounty

A program that rewards external researchers for responsibly reporting valid security vulnerabilities.

Bundler (ERC-4337)

Service packaging user operations into transactions for account-abstraction wallets.

Burn (Token)

Also: coin burn

Permanently removing tokens from circulation, often to reduce supply or pay fees.

Business Continuity Plan (BCP)

Documented procedures to maintain or quickly resume critical operations during and after disruptive incidents.

Business Email Compromise (BEC)

Fraud that impersonates executives or vendors to trick employees into wiring funds or sharing sensitive data.

Byzantine Attack

Malicious behavior by nodes sending conflicting or false messages in a distributed network.

Byzantine Fault Tolerance (BFT)

Also: BFT

Ability of a distributed system to reach agreement despite some nodes failing or acting maliciously.

Canary Token

A deceptive asset such as a fake file or credential that triggers alerts when accessed, indicating possible intrusion.

Central Bank Digital Currency (CBDC)

Also: CBDC

Digital money issued by a central bank, distinct from decentralized cryptocurrencies and often designed for retail or wholesale settlement.

Certificate Authority (CA)

Also: CA

A trusted entity that issues digital certificates, binding public keys to identities and enabling secure TLS/SSL communication on the web.

Certificate Pinning

Associating a host with expected certificate or public key values to prevent impersonation by rogue CAs or MitM attackers.

Certificate Revocation List (CRL)

A signed list of digital certificates that have been invalidated before their expiration date.

CEX (Centralized Exchange)

A company-operated exchange that custodies user funds and matches orders.

Chain ID

Numeric identifier preventing replay of signed transactions across different EVM networks.

Chain of Custody

Documented handling of digital evidence from collection through analysis to ensure admissibility and integrity in investigations.

Chain Reorganization

Also: reorg

When a longer chain replaces recent blocks, reversing transactions in the orphaned fork.

Checkpoint

A trusted or finalized block height after which history is considered settled.

Chief Information Security Officer (CISO)

An executive responsible for an organization's information security strategy, risk management, and security program.

CI/CD Pipeline

Also: continuous integration, continuous delivery

Automated stages that build, test, and deploy software on every change, reducing manual release work and drift between environments.

CIA Triad

Also: Confidentiality Integrity Availability

A foundational security model based on three principles: Confidentiality (protecting data from unauthorized disclosure), Integrity (preventing unauthorized modification), and Availability (ensuring timely, reliable access).

Circulating Supply

Coins or tokens publicly available and trading, excluding locked or burned amounts.

Circulating Supply vs Total Supply

Total supply is all minted tokens; circulating excludes team locks, treasuries, or burns.

CIS Critical Security Controls

A prioritized set of safeguards published by CIS to defend against common attacks and improve security hygiene.

Cleartext

Data transmitted or stored without encryption, readable to anyone who intercepts or accesses it.

Clickjacking

Tricking users into clicking hidden or disguised UI elements, often via transparent overlays on malicious pages.

Clipboard Hijacking

Malware that swaps copied wallet addresses so victims send funds to attackers.

Cloud Access Security Broker (CASB)

A policy enforcement point between users and cloud services, providing visibility, compliance, and threat protection.

Cloud Security Posture Management (CSPM)

Continuous assessment of cloud configurations against security best practices to find misconfigurations and compliance gaps.

Cloud-Native

Applications and practices designed for elastic scaling, containers, and managed cloud services rather than lift-and-shift of monoliths.

CMMC

Cybersecurity Maturity Model Certification — US DoD framework requiring graded security practices in the defense supply chain.

CoinJoin

A privacy technique combining multiple users' payments to obscure which inputs paid which outputs.

Cold Boot Attack

Extracting encryption keys from RAM by rebooting or cooling memory chips before contents decay.

Cold Wallet

Also: cold storage

Cryptocurrency storage kept offline on hardware or paper to reduce exposure to online theft and malware.

Collateralized Debt Position (CDP)

A DeFi position locking collateral to mint stablecoins or borrow assets.

Command and Control (C2)

Also: C2, CnC

Infrastructure attackers use to send instructions to compromised hosts and receive stolen data.

Commit-Reveal Scheme

Submitting a hidden commitment first, then revealing data later to prevent front-running in auctions or voting.

Commitment Scheme

Cryptographic promise to a value revealed later, used in rollups and auctions.

Compliance (Security)

Adherence to laws, regulations, and standards such as GDPR, HIPAA, or PCI DSS through documented controls and audits.

Composability

Ability to combine DeFi protocols like money legos in single transactions.

Computer Security Incident Response Team (CSIRT)

A specialized team that coordinates detection, analysis, containment, and recovery from security incidents.

Confidential Computing

Hardware-based isolation such as trusted execution environments that protect data in use from the host operating system.

Confidential Transaction

Hiding transaction amounts on-chain while still proving balances are valid.

Consensus Finality

Also: finality

The point at which a block or transaction cannot realistically be reversed under network rules.

Consensus Mechanism

Also: consensus algorithm

Rules by which a blockchain network agrees on the valid ordering and content of blocks, such as proof of work or proof of stake.

Constant Product Formula

Also: x*y=k

x*y=k AMM curve used by Uniswap-style pools for automatic pricing.

Container Escape

Breaking out of a container sandbox to access the host or other containers, often via kernel vulnerabilities.

Container Orchestration

Automated scheduling, scaling, networking, and recovery of containers across a cluster, commonly with Kubernetes.

Container Security

Securing images, runtimes, orchestrators, and networks used in containerized workloads, including least privilege and image scanning.

Content Disarm and Reconstruction (CDR)

Technology that removes active content from files and rebuilds safe versions to block embedded malware.

Content Security Policy (CSP)

An HTTP header that restricts which scripts, styles, and other resources a browser may load, mitigating XSS.

Context Window

The maximum amount of text (tokens) a language model can consider in one request, including prompts, documents, and prior conversation.

Continuous Monitoring

Ongoing observation of systems and controls to detect drift, misconfigurations, and suspicious activity in near real time.

Control Framework

Structured guidance such as NIST CSF or ISO 27001 that organizes security controls and improvement activities.

Covert Channel

A hidden communication path that violates security policy, such as timing or storage signals between isolated processes.

Credential Dumping

Also: LSASS dumping

Extracting authentication secrets from memory or storage on a compromised system, often preceding lateral movement.

Credential Stuffing

Automated login attempts using username-password pairs leaked from other breaches.

Cross-Chain Messaging

Protocols passing arbitrary data or commands between blockchains beyond simple token bridges.

Cross-Site Request Forgery (CSRF)

Forcing an authenticated user's browser to perform unwanted actions on a site they trust, such as changing account settings.

Cross-Site Scripting (XSS)

Also: XSS

A vulnerability that allows attackers to inject malicious scripts into web pages viewed by other users, often to steal sessions or deface content.

Cryptocurrency

Also: crypto

Digital assets secured by cryptography and typically recorded on a blockchain, used for payments, speculation, or protocol incentives.

Cryptocurrency Wallet

Also: crypto wallet

Software or hardware that stores keys and lets users send, receive, and view balances on one or more blockchains.

Cryptographic Key

Secret or private data used with an algorithm to encrypt, decrypt, sign, or verify information.

Cryptography

The practice of securing communication and data through mathematical techniques — including encryption, hashing, digital signatures, and key exchange.

Cryptojacking

Unauthorized use of victim computing resources to mine cryptocurrency, often via malware or compromised web scripts.

Custodial Exchange

An exchange that holds private keys and funds on behalf of users.

Custody Risk

Risk that a custodian loses, steals, or blocks access to held cryptocurrency.

CVE

Also: Common Vulnerabilities and Exposures

Common Vulnerabilities and Exposures — a standardized identifier for publicly known cybersecurity vulnerabilities, maintained to improve tracking and coordination across tools and vendors.

CVSS

Also: Common Vulnerability Scoring System

Common Vulnerability Scoring System — a standardized way to rate the severity of vulnerabilities for prioritization.

CWE

Also: Common Weakness Enumeration

Common Weakness Enumeration — a catalog of software and hardware weakness types that can lead to vulnerabilities.

Cyber Insurance

Insurance coverage for costs related to breaches, ransomware, business interruption, and legal liabilities.

Cyber Kill Chain

A model describing stages of intrusions from reconnaissance through actions on objectives, used to design layered defenses.

Cyber Resilience

The ability to prepare for, withstand, recover from, and adapt to adverse cyber events while continuing critical functions.

DApp Browser

A wallet or browser interface that connects to decentralized applications via Web3 providers.

Dark Web

Overlay networks requiring special software where stolen data, tools, and illicit services are traded.

Data at Rest

Information stored on disk, databases, or backups, protected with encryption, access controls, and secure disposal.

Data Availability

Also: DA

Guarantee that block data needed to verify transactions is published and retrievable by nodes.

Data Breach

An incident where sensitive data is accessed, disclosed, or acquired without authorization.

Data Classification

Labeling information by sensitivity to apply appropriate handling, storage, and sharing controls.

Data Exfiltration

Also: exfil

The unauthorized transfer of data from a system or network to an external destination controlled by an attacker.

Data Governance

Policies and processes that ensure data quality, lawful use, retention, and protection across an organization.

Data in Transit

Information moving across networks, typically protected with TLS, VPNs, or message-level encryption.

Data Loss Prevention (DLP)

Tools and policies that detect and block unauthorized movement or exposure of sensitive data.

Data Minimization

Collecting and retaining only the personal or sensitive data necessary for a stated purpose.

Data Poisoning

Manipulating training or operational data to degrade or bias machine learning systems and security analytics.

Decentralized Application (DApp)

Also: DApp

An application whose backend logic runs on a blockchain or peer network rather than solely on centralized servers.

Decentralized Autonomous Organization (DAO)

Also: DAO

A community-governed organization whose rules and treasury actions are encoded in smart contracts and voted on by token holders.

Decentralized Exchange (DEX)

Also: DEX

A marketplace for swapping tokens without a traditional custodial intermediary, often using automated liquidity pools.

Decentralized Finance (DeFi)

Also: DeFi

Financial services such as lending, trading, and yield built on smart contracts and public blockchains instead of banks.

Decentralized Identifier (DID)

Also: DID

A globally unique identifier controlled by the holder, often used in Web3 identity.

Decentralized Physical Infrastructure (DePIN)

Also: DePIN

Token-incentivized networks for real-world infrastructure such as storage, wireless, or sensors.

Decentralized Storage

File storage spread across a network with cryptographic proofs, e.g. IPFS, Filecoin, or Arweave.

Decryption

Converting ciphertext back into readable plaintext using the correct key or password.

Deep Packet Inspection (DPI)

Examining packet contents beyond headers to enforce policy, detect threats, or shape traffic.

Deepfake

Synthetic audio, video, or images generated by AI that convincingly impersonate real people, used in fraud and disinformation.

Default Credentials

Factory usernames and passwords left unchanged on devices or applications, a common entry point for attackers.

Defense Evasion

Techniques attackers use to avoid detection, such as disabling logs, obfuscating malware, or blending with legitimate traffic.

Defense in Depth

Layering multiple independent security controls so that failure of one layer does not result in total compromise.

Delegated Proof of Stake (DPoS)

Also: DPoS

Stakeholders vote for a small set of delegates to produce blocks on their behalf.

Delegated Staking

Token holders delegate stake to validators and share rewards minus fees.

Dencun Upgrade

Ethereum 2024 upgrade introducing blob transactions and proto-danksharding for L2 scaling.

Denial of Service (DoS)

Also: DoS, DDoS, Distributed Denial of Service

An attack that overwhelms a system, service, or network with traffic or requests so legitimate users cannot access it. Distributed variants (DDoS) use many sources.

Deterministic Wallet

Wallet generating keys from a single seed, synonymous with HD wallet in practice.

DevSecOps

Integrating security practices, tooling, and culture into software development and delivery pipelines.

Dictionary Attack

Guessing passwords using a list of common words and previously leaked passwords, faster than full brute force.

Difficulty Adjustment

Algorithm that changes mining difficulty to keep block times stable as hash rate shifts.

Difficulty Bomb

Ethereum mechanism gradually increasing PoW difficulty to encourage migration to proof of stake.

Diffie-Hellman

A key exchange protocol that allows parties to establish a shared secret over an insecure channel.

Digital Certificate

An electronic document signed by a CA that binds a public key to an identity, enabling trusted TLS and code signing.

Digital Forensics

Scientific collection and analysis of digital evidence from computers, mobile devices, networks, and cloud environments.

Digital Signature

A cryptographic proof that data was created or approved by the holder of a private key and was not altered.

Digital Twin

A live virtual model of a physical system fed by real-time data, used for simulation, monitoring, and predictive maintenance.

Directory Traversal

Also: path traversal

Exploiting insufficient path validation to read or write files outside the intended web root.

Disaster Recovery Plan (DRP)

Procedures and infrastructure to restore IT systems and data after major outages or destructive attacks.

DMZ

Demilitarized Zone — a network segment that exposes public-facing services while isolating internal systems behind additional controls.

DNS Security

Protecting domain name resolution through DNSSEC, monitoring, filtering, and detecting tunneling or hijacking.

DNS Spoofing

Also: DNS cache poisoning

Returning false DNS answers to redirect users to malicious sites or intercept traffic.

DNS Tunneling

Encoding data in DNS queries and responses to bypass firewalls and exfiltrate information covertly.

DNSSEC

Extensions that cryptographically sign DNS records to prevent tampering and spoofing of responses.

Domain Controller

A Windows server that authenticates users and enforces security policy in an Active Directory domain.

Double Spending

Spending the same digital coin twice, which blockchain consensus mechanisms are designed to prevent.

Downgrade Attack

Forcing use of weaker protocols or ciphers, such as obsolete TLS versions, to simplify exploitation.

DREAD

A qualitative risk rating model for threats: Damage, Reproducibility, Exploitability, Affected users, and Discoverability.

Drive-by Download

Malware installed when a user visits a compromised or malicious website without explicit consent.

Dusting Attack

Sending tiny amounts of crypto to many addresses to deanonymize wallets when they are later spent together.

EASM

Also: External Attack Surface Management

External Attack Surface Management — discovering and monitoring internet-exposed assets, misconfigurations, and vulnerabilities.

eBPF

Also: extended Berkeley Packet Filter

A Linux kernel technology for running sandboxed programs on events such as network packets and syscalls, widely used for observability and security.

Edge Computing

Processing data near where it is created (devices, gateways, local sites) to cut latency and reduce sending raw data to the cloud.

EDR

Also: Endpoint Detection and Response

Endpoint Detection and Response — agents on hosts that collect telemetry, detect threats, and support investigation and containment.

EIP (Ethereum Improvement Proposal)

A formal proposal describing new features or standards for Ethereum.

EIP-1559

Ethereum fee market change with base fee burn and priority tips to validators.

Elliptic Curve Cryptography (ECC)

Public-key cryptography based on elliptic curves, offering strong security with smaller keys than traditional RSA.

Email Authentication (SPF, DKIM, DMARC)

Standards that verify senders and instruct receivers how to handle spoofed mail, reducing phishing and BEC.

Email Spoofing

Forging the From address or domain of messages to appear as a trusted sender.

Embedding

Also: vector embedding

A numerical vector representation of text, images, or other data so that similar items sit close together in vector space for search and ML.

Encryption

The process of encoding data so that only parties with the correct key can read it. Protects confidentiality in transit and at rest.

Encryption at Rest

Protecting stored data with algorithms such as AES, often combined with key management and access controls.

Encryption in Transit

Protecting data moving between systems using protocols such as TLS or IPsec.

Endpoint Security

Controls on laptops, servers, and mobile devices including hardening, EDR, patching, and application control.

ENS (Ethereum Name Service)

Maps human-readable names like name.eth to wallet addresses and other records.

Enumeration

Systematic discovery of users, services, shares, or resources on a target to plan further attacks.

Epoch (Staking)

Fixed period in proof-of-stake for validator duties, rewards, and checkpointing.

ERC-1155

Multi-token standard supporting fungible and non-fungible assets in one contract.

ERC-20

Fungible token standard on Ethereum used by most altcoins and DeFi tokens.

ERC-4337

Ethereum standard for account abstraction using user operations, paymasters, and bundlers.

ERC-721

Non-fungible token standard for unique on-chain assets.

Ethereum

Also: ETH

A programmable blockchain supporting smart contracts, DeFi, and NFTs, now using proof of stake.

Ethereum Virtual Machine (EVM)

The stack-based runtime that executes smart contract bytecode on Ethereum-compatible chains.

Ethical Hacking

Authorized security testing performed to find and fix vulnerabilities before malicious exploitation.

Evasion Techniques

Methods malware and attackers use to avoid antivirus, sandboxes, and analysts, including packing and living off the land.

Event Log (EVM)

Indexed contract outputs used by dApps and indexers to track on-chain activity.

Exit Scam

Project founders disappearing after raising funds or draining liquidity, leaving investors with worthless tokens.

Exploit

Code or technique that takes advantage of a vulnerability to achieve unintended behavior such as code execution or access.

Exploit (Smart Contract)

Also: DeFi exploit

Abuse of a bug or design flaw in contract code to steal funds or manipulate protocol state.

Extended Detection and Response (XDR)

Correlating telemetry across endpoints, network, email, and cloud into unified detection and response workflows.

Fail Secure

Design where a failure defaults to a safe state, such as denying access when a controller is offline.

False Positive

A security alert incorrectly indicating malicious activity, consuming analyst time and eroding trust in tools.

Faucet (Testnet)

Service dispensing free testnet coins for developers.

Fee Market

Mechanism allocating scarce block space to highest-paying transactions.

Fiat On-Ramp

Service converting traditional currency into cryptocurrency for new users.

FIDO2

Standards for phishing-resistant passwordless authentication using hardware security keys or platform authenticators.

File Integrity Monitoring (FIM)

Detecting unauthorized changes to critical files and configurations by comparing hashes or attributes.

Fileless Malware

Malicious activity that runs in memory or abuses trusted tools without leaving a traditional executable on disk.

Finality Gadget

Component that marks blocks as irreversible, often used with proof-of-stake checkpoints.

Fine-Tuning

Further training of a pre-trained model on a smaller, task-specific dataset so it behaves better for a particular domain or use case.

Firewall

A network security device or software that monitors and controls incoming and outgoing traffic based on predefined security rules.

Flash Loan

Uncollateralized loan that must be borrowed and repaid within a single transaction or it reverts.

Flashbots

Infrastructure for private transaction submission and MEV mitigation on Ethereum.

Floor Price (NFT)

The lowest listed price for an NFT in a collection on a marketplace.

Forensic Imaging

Creating bit-for-bit copies of storage media while preserving evidence integrity and chain of custody.

Fork (Blockchain)

A divergence in chain history into two competing versions, intentional or accidental.

Forward Secrecy

Also: perfect forward secrecy

Property of key exchange where compromise of long-term keys does not decrypt past session traffic.

Foundation Model

A large model trained on broad data that can be adapted for many downstream tasks through prompting, fine-tuning, or tooling.

Fragmentation Attack

Abusing IP or protocol fragmentation to evade firewalls or reassemble malicious payloads.

Fraud Proof

Evidence submitted on Layer 2 that a posted state transition was invalid.

Front-Running

Placing a transaction ahead of a known pending trade to profit from the price move it will cause.

Frontrunning Protection

Designs such as private mempools or batch auctions reducing MEV on user trades.

Full Disk Encryption (FDE)

Encrypting entire storage volumes so data remains protected if a device is lost or stolen.

Full Node

A node that downloads and validates all blocks and state, enforcing network rules independently.

Fungible Token

Interchangeable token units where each unit is equivalent to another of the same type.

Fuzzing

Automated testing that sends malformed or random inputs to software to uncover crashes and security flaws.

Gas Fee

Also: transaction fee, gas

A fee paid to validators or miners to include a transaction in a block, often varying with network congestion and computation cost.

Gas Limit

Maximum computation units a block or transaction may consume on EVM chains.

Gas War

Users bidding extremely high gas fees to win scarce allocation such as NFT mints.

Gasless Transaction

User-facing transaction where a relayer or paymaster covers gas costs.

GDPR

General Data Protection Regulation — EU law governing personal data processing, breach notification, and individual rights.

Generative AI

Also: GenAI

AI that creates new content such as text, code, images, or audio from prompts, as opposed to only classifying or predicting labels.

Genesis Block

The first block in a blockchain, hard-coded or specially configured at network launch.

GitOps

Operating infrastructure and applications from Git as the source of truth, with automated reconciliation when the cluster drifts from declared config.

Governance Proposal

On-chain or off-chain vote to change protocol settings, treasury spending, or upgrades.

Governance Token

Token granting holders voting rights over protocol parameters, treasury, or upgrades.

GPG

GNU Privacy Guard — open-source implementation of OpenPGP for email and file encryption and signing.

GraphQL

An API query language where clients request exactly the fields they need, often replacing multiple REST calls with one structured request.

Gray Hat

Security research that may operate without explicit authorization but often reports findings rather than causing harm.

Greyware

Programs that are not clearly malicious but behave undesirably, such as adware or nuisance toolbars.

Griefing Attack

Harming a protocol or users without direct profit, e.g. wasting gas or blocking actions.

Gwei

One billionth of an ether, commonly used to quote Ethereum gas prices.

Hallucination (AI)

Also: model hallucination

When a model states false or unsupported information with high confidence, a key risk in assistants, search, and automated decisions.

Halving

Also: block reward halving

Periodic reduction of Bitcoin block rewards, roughly every four years, tightening issuance.

Hard Fork

A breaking protocol change requiring all nodes to upgrade; non-upgraded chains may split.

Hardware Security Module (HSM)

A tamper-resistant device that generates, stores, and performs operations with cryptographic keys.

Hash Collision

Two different inputs producing the same hash value, undermining integrity guarantees if exploitable.

Hash Rate

Total computational power mining a proof-of-work network, measured in hashes per second.

Hashing

Also: hash

A one-way function that maps input data to a fixed-size digest. Used for integrity checks and storing passwords securely (with salt and slow algorithms).

HD Wallet

Hierarchical deterministic wallet deriving many addresses from one seed phrase using BIP-32 paths.

Heap Overflow

Memory corruption on the heap that can overwrite metadata and enable code execution in native applications.

Heap Spraying

Placing shellcode at predictable heap locations to increase reliability of memory corruption exploits.

HIPAA

US Health Insurance Portability and Accountability Act — security and privacy rules for protected health information.

HMAC

Hash-based Message Authentication Code — verifies integrity and authenticity of a message using a secret key and hash function.

Homograph Attack

Also: IDN homograph attack

Using visually similar Unicode characters in domains or filenames to deceive users.

Honeypot

A decoy system designed to attract attackers and gather intelligence on tools, tactics, and sources.

Honeypot (Smart Contract)

Trap contract appearing profitable but blocking attackers from withdrawing while allowing deposits.

Host-Based Firewall

Firewall software on an endpoint that filters traffic to and from that machine.

Hot Storage Risk

Risk from keeping keys or large balances in internet-connected wallets or exchange accounts.

Hot Wallet

A cryptocurrency wallet connected to the internet for convenience, carrying higher risk than offline cold storage.

HTTP Strict Transport Security (HSTS)

A policy forcing browsers to use HTTPS for a site, reducing SSL stripping and cookie hijacking risks.

HTTP/3

The latest major HTTP version, running over QUIC instead of TCP, to improve performance on lossy networks and reduce connection setup delay.

HTTPS

HTTP secured with TLS, providing encryption and server authentication for web traffic.

Hypervisor Security

Protecting virtualization layers from VM escape, misconfiguration, and unauthorized access to host resources.

ICO (Initial Coin Offering)

Early fundraising by selling tokens to the public, often before a working product exists.

Identification

Claiming an identity, distinct from verification; the first step before authentication.

Identity and Access Management (IAM)

Also: IAM

Framework of policies and technologies for managing digital identities, authentication, and authorization.

Identity Federation

Trust relationships that let users authenticate once and access multiple organizations' systems with federated identities.

Identity Provider (IdP)

A service that authenticates users and issues assertions to relying applications, often via SAML or OIDC.

IDO (Initial DEX Offering)

Token launch conducted on a decentralized exchange, often via liquidity pool creation.

Immutable Ledger

The property that confirmed blockchain records are extremely difficult to alter without network consensus, supporting auditability.

Impermanent Loss

Also: IL

Loss LPs face versus holding assets when pool prices diverge from deposit ratios.

Incident Classification

Categorizing security events by type, severity, and impact to prioritize response and reporting.

Incident Containment

Short-term actions to limit spread of an attack, such as isolating hosts, blocking indicators, or disabling accounts.

Incident Response

Also: IR

The organized approach to addressing and managing the aftermath of a security breach or cyberattack — including detection, containment, eradication, recovery, and lessons learned.

Index Fund (On-Chain)

Token tracking a basket of assets, often rebalanced by a protocol.

Indicator of Attack (IOA)

Also: IOA

Patterns of behavior that suggest an attack is in progress, focusing on adversary intent rather than static artifacts.

Indicator of Compromise (IoC)

Also: IoC, Indicators of Compromise

Forensic artifacts such as IP addresses, file hashes, or domain names that suggest a system may have been breached.

Infinite Token Approval

Granting a contract unlimited spend rights on a token, dangerous if the contract is compromised.

Inflation (Token)

Increasing token supply over time through emissions, staking rewards, or mining.

Information Disclosure

Unintended exposure of sensitive data through errors, misconfigurations, or vulnerable applications.

Information Security

Protecting confidentiality, integrity, and availability of information through governance, technology, and processes.

Infrastructure as Code (IaC)

Also: IaC

Defining servers, networks, and cloud resources in versioned files (e.g. Terraform, CloudFormation) so environments are reproducible and reviewable.

Infrastructure as Code Security

Securing Terraform, CloudFormation, and similar definitions against secrets leakage, overly permissive policies, and drift.

Inscription (Bitcoin)

Arbitrary data embedded on a satoshi via the Ordinals protocol.

Insecure Direct Object Reference (IDOR)

Accessing objects by modifying identifiers in requests without proper authorization checks.

Insider Threat

Risk posed by employees, contractors, or partners who misuse legitimate access maliciously or negligently.

Intent-Based Architecture

Users sign desired outcomes; solvers compete to fulfill them optimally.

Inter-Blockchain Communication (IBC)

Cosmos protocol for relaying packets and tokens between sovereign blockchains.

Intrusion Detection System (IDS)

Also: IDS, IPS, Intrusion Prevention System

A tool that monitors network or host activity for malicious behavior or policy violations and generates alerts. An IPS can also block traffic.

Intrusion Prevention System (IPS)

Inline security device that detects malicious activity and can automatically block matching traffic.

IP Spoofing

Forging the source IP address in packets, used in reflection attacks or impersonation on trusted networks.

IPFS

Distributed content-addressed storage often used to host NFT metadata and dApp frontends.

IPsec

A suite of protocols that authenticates and encrypts IP packets, commonly used in VPNs and site-to-site tunnels.

ISO/IEC 27001

International standard for establishing, implementing, and certifying an information security management system.

Jailbreaking

Removing manufacturer restrictions on mobile devices, increasing attack surface and bypassing security controls.

Kerberoasting

Offline cracking of Kerberos service ticket material to recover service account passwords in Active Directory.

Kerberos

A network authentication protocol using tickets and symmetric cryptography, central to Active Directory environments.

Key Derivation Path

Also: derivation path

BIP-44 path specifying how HD wallets generate addresses per coin and account.

Key Exchange

Protocols such as Diffie-Hellman or ECDH that establish shared secrets for encrypted communication.

Key Management

Lifecycle controls for generating, storing, rotating, backing up, and revoking cryptographic keys.

Keylogger

Software or hardware that records keystrokes to steal passwords and other sensitive input.

KYC (Know Your Customer)

Also: crypto KYC

Identity verification required by regulated exchanges before trading or withdrawals.

Large Language Model (LLM)

Also: LLM

A neural network trained on vast text corpora to predict and generate language, powering chatbots, coding assistants, and summarization tools.

Lateral Movement

Techniques attackers use to navigate from one compromised system to others within a network.

Layer 0

Also: L0

Base interoperability layer connecting multiple Layer 1 chains, e.g. Cosmos hubs or Polkadot relay.

Layer 1

Also: L1

The base blockchain layer such as Bitcoin, Ethereum, or Solana that settles its own security.

Layer 2

Also: L2

Protocols built on top of a base blockchain to increase throughput or lower fees while inheriting its security assumptions.

Layer 3

Also: L3

Application-specific chain stacked on a Layer 2 for even cheaper or customized execution.

LDAP Injection

Manipulating LDAP queries through unsanitized input to bypass authentication or access directory data.

Least Privilege

Also: principle of least privilege

The principle that users, applications, and systems should receive only the minimum access rights necessary to perform their functions.

Light Client

A wallet or node that verifies minimal data, often via headers or proofs, without full chain download.

Lightning Network

Bitcoin Layer 2 payment channel network for fast, low-fee off-chain transactions.

Liquid Staking

Staking while receiving a liquid receipt token tradable in DeFi, e.g. stETH.

Liquid Staking Token

Also: LST

Receipt token representing staked assets plus accrued rewards.

Liquidation (DeFi)

Forced sale of collateral when a loan's health factor falls below a protocol threshold.

Liquidity Mining

Rewarding users with tokens for providing liquidity to pools or protocols.

Liquidity Pool

Pooled tokens locked in a smart contract that enable decentralized trading and often pay fees or rewards to liquidity providers.

Liquidity Provider (LP)

Also: LP

User who deposits assets into pools enabling trading and earns fees or incentives.

Liquidity Token (LP Token)

Receipt token representing a share of a liquidity pool, redeemable for underlying assets.

Living off the Land

Also: LOLBAS, LOT L

Using legitimate system tools and binaries already present on hosts to execute attacks and evade detection.

Log Tampering

Altering or deleting audit and security logs to hide traces of malicious activity.

Logic Bomb

Malicious code that triggers when a defined condition occurs, such as a date or user action.

Long-Range Attack

PoS attack rewriting history from genesis using old stake unless checkpoints prevent it.

MAC Address Spoofing

Changing a network interface's hardware address to impersonate another device or bypass access controls.

Mainnet

The live production blockchain where real assets have value, as opposed to testnets.

Malvertising

Malicious or compromised online advertisements that redirect users to exploits or malware downloads.

Malware

Malicious software designed to disrupt, damage, or gain unauthorized access — including viruses, worms, trojans, ransomware, and spyware.

Man-in-the-Middle (MitM)

Also: MitM, MiTM

An attack where the adversary secretly relays or alters communication between two parties who believe they are talking directly to each other.

Managed Detection and Response (MDR)

Outsourced service combining technology and analysts to monitor environments and respond to threats.

Mandatory Access Control (MAC)

Access control where a central policy defines classifications and clearance, common in high-assurance systems.

Market Cap (Crypto)

Circulating supply multiplied by price, a rough size metric for coins or tokens.

Max Supply

Hard cap on how many tokens can ever exist for a cryptocurrency.

Maximal Extractable Value (MEV)

Also: MEV

Profit validators or searchers can capture by reordering, inserting, or censoring transactions within a block.

Memecoin

Token driven mainly by community hype and internet culture rather than utility.

Memory Safety

Language and runtime properties that prevent common flaws like buffer overflows through bounds checking.

Mempool

Also: transaction pool

Set of unconfirmed transactions waiting to be included in the next block.

Merkle Proof

Compact proof that a transaction or piece of state is included in a block's Merkle root.

Merkle Tree

A hash tree that lets blockchains prove a transaction is included in a block without storing every transaction in a single hash.

Meta-Transaction

Transaction where a relayer pays gas and the user signs intent, improving onboarding UX.

Metadata Leakage

Exposure of sensitive information in file properties, headers, or telemetry rather than primary content.

MEV Boost

Middleware allowing Ethereum validators to access external block builders and MEV payments.

MFA Fatigue Attack

Also: MFA bombing

Bombarding a user with push MFA prompts until they approve one out of annoyance, granting the attacker access.

MiCA

EU Markets in Crypto-Assets regulation governing issuance, exchanges, and stablecoins in Europe.

Microsegmentation

Dividing networks into fine-grained zones with strict policies to limit lateral movement.

Microservices Architecture

Building an application as many small, independently deployable services that communicate over APIs, trading simplicity for scalability and team autonomy.

Mining (Blockchain)

Also: crypto mining

Competing to solve a proof-of-work puzzle or validate blocks in exchange for block rewards and fees on a cryptocurrency network.

Mining Pool

Miners combine hash power and split rewards by contribution to reduce payout variance.

Mint and Burn Bridge

Bridge locking assets on source chain and minting wrapped tokens on destination.

Minting (NFT)

Creating a new NFT on-chain, usually by paying gas and invoking a contract function.

MITRE ATT&CK

Also: ATT&CK

A knowledge base of adversary tactics and techniques based on real-world observations, used for detection and purple teaming.

Mixer

Also: tumbler

Service that pools deposits and redistributes to obscure transaction trails, raising AML concerns.

Mobile Application Security

Protecting iOS and Android apps through secure storage, transport, code hardening, and API controls.

Mobile Device Management (MDM)

Administration of smartphones and tablets through policies, remote wipe, and application control.

Model Context Protocol (MCP)

Also: MCP

An open standard for connecting AI assistants to external tools and data sources through a consistent client–server interface.

Modular Blockchain

Architecture separating execution, consensus, and data availability into specialized layers.

Multi-Cloud Security

Governance and controls spanning multiple cloud providers to ensure consistent policy and visibility.

Multi-Factor Authentication (MFA)

Also: MFA, 2FA, two-factor authentication

Authentication that requires two or more independent factors — something you know, have, or are — reducing risk if one factor is compromised.

Multi-Signature Wallet

Also: multisig

Wallet requiring M-of-N signatures to move funds, reducing single-key risk.

Multichain

Also: multi-chain

Ecosystem of multiple blockchains requiring bridges, messaging, and wallet support.

Multimodal AI

Models that accept and produce more than one modality, such as text plus images, audio, or video, in a single system.

Nakamoto Consensus

Bitcoin-style consensus combining proof of work, longest chain rule, and decentralized block production.

NAT

Network Address Translation — maps private addresses to public ones, affecting visibility and some attack paths.

Network Access Control (NAC)

Enforcing device health and identity checks before granting access to a corporate network.

Network Forensics

Capturing and analyzing traffic and flow data to reconstruct incidents and identify malicious communication.

Network Segmentation

Dividing networks into isolated segments to contain breaches and enforce least privilege traffic flows.

Next-Generation Firewall (NGFW)

A firewall that adds application awareness, intrusion prevention, and threat intelligence to traditional packet filtering.

NIST Cybersecurity Framework

Guidance organized around Identify, Protect, Detect, Respond, and Recover for managing cybersecurity risk.

Node Operator

Entity running validator or RPC infrastructure, often for staking services.

Node Syncing

Process of a new node downloading and validating historical blockchain data.

Non-Custodial Wallet

Also: self-custody wallet

A wallet where the user alone controls private keys, as opposed to an exchange or service holding funds on their behalf.

Non-Fungible Token (NFT)

Also: NFT

A unique on-chain token representing ownership or rights to a digital or linked physical asset, unlike interchangeable coins.

Non-Human Identity (NHI)

Also: machine identity

Machine identities such as service accounts, API keys, bots, and workloads that need lifecycle management like human users.

Non-Repudiation

Assurance that a party cannot deny having performed an action, often supported by digital signatures and audit trails.

Nonce (Blockchain)

A number miners vary to find a valid block hash, or a transaction counter for an account.

Nothing-at-Stake Problem

Theoretical PoS issue where validators might sign multiple forks at little cost without slashing.

OAuth

An authorization framework that lets applications obtain limited access to user accounts without handling passwords directly.

Observability

The ability to understand system health from exported telemetry—metrics, logs, and traces—especially in distributed and cloud environments.

Off-Chain Governance

Votes conducted via forums, snapshots, or multisigs rather than entirely on-chain.

OIDC

OpenID Connect — an identity layer on OAuth 2.0 for authentication and single sign-on using ID tokens.

Ommer Block

Also: uncle block

Valid block not included in the main chain, formerly called uncle block on Ethereum PoW.

On-Chain Governance

Protocol changes executed automatically after token-holder votes pass thresholds.

On-Chain Token

Also: crypto token

A digital unit defined by a blockchain protocol or smart contract, such as a native coin, governance token, or stablecoin.

Open Source Intelligence (OSINT)

Collecting and analyzing publicly available information to support security assessments and investigations.

OpenTelemetry

Also: OTel

A vendor-neutral standard and toolkit for collecting traces, metrics, and logs from applications and infrastructure.

Operational Technology (OT) Security

Protecting industrial control systems, SCADA, and physical processes from cyber-physical threats.

Optimistic Oracle

Oracle assuming data is correct unless disputed within a challenge period.

Optimistic Rollup

Layer 2 that assumes transactions are valid unless challenged during a dispute window.

Oracle (Blockchain)

A service that feeds off-chain data such as prices or weather into smart contracts, introducing trust and manipulation risks if flawed.

Oracle Manipulation

Also: oracle attack

Attack that distorts price feeds a DeFi protocol relies on to trigger unfair liquidations or loans.

Order Book DEX

Decentralized exchange matching bids and asks, sometimes with off-chain matching.

Out-of-Band Attack

Extracting data or triggering effects through a channel separate from the primary request-response path.

Overcollateralized Loan

Loan requiring collateral worth more than the borrowed amount to protect lenders.

OWASP

Also: Open Web Application Security Project

The Open Worldwide Application Security Project — a community that publishes guidance such as the OWASP Top 10 list of critical web application risks.

PAM

Also: Privileged Access Management

Privileged Access Management — controls for elevated accounts including vaulting, session recording, and just-in-time access.

Parachain

Polkadot slot chain that shares security from the relay chain while running its own logic.

Pass-the-Hash

Using captured password hashes to authenticate without cracking the plaintext password.

Pass-the-Ticket

Reusing stolen Kerberos tickets to access resources in Active Directory environments.

Passkey

A phishing-resistant login credential stored on a device or sync provider, based on FIDO2/WebAuthn instead of reusable passwords.

Password Policy

Rules governing password length, complexity, rotation, and lockout to reduce credential guessing risk.

Password Spraying

Trying a few common passwords against many accounts to avoid lockouts triggered by brute force.

Patch Management

The process of identifying, testing, and deploying updates to software and systems to fix vulnerabilities and maintain stability.

Payload

The component of an attack that performs the intended malicious action after delivery or exploitation.

Paymaster

Contract or service sponsoring gas fees for users in account-abstraction flows.

Payment Channel

Off-chain channel between parties settled on-chain only when opened, closed, or disputed.

PCI DSS

Payment Card Industry Data Security Standard — requirements for organizations that store, process, or transmit cardholder data.

Peg Mechanism

Design keeping a token near a target price via reserves, arbitrage, or algorithms.

Pegged Asset

Token whose value is intended to track another asset such as USD or BTC via reserves or algorithms.

Penetration Testing

Also: pen test, pentest

Authorized simulated attacks against systems or applications to discover exploitable weaknesses before malicious actors do.

Permissioned Blockchain

Ledger where only approved entities may read, write, or validate, common in enterprise.

Permissionless Blockchain

Anyone can run a node, validate, or use the network without gatekeepers.

Perpetual Futures (Crypto)

Also: perps

Derivative contract with no expiry, using funding rates to keep price near the spot index.

PGP

Pretty Good Privacy — encryption and signing for email and files, implemented in tools such as GPG.

Pharming

Redirecting users to fraudulent sites via DNS manipulation or hosts file changes rather than deceptive links.

Phishing

Also: spear phishing, smishing, vishing

Social engineering that tricks users into revealing sensitive information or installing malware, often via deceptive email, SMS (smishing), or voice (vishing).

Pivoting

Using a compromised host as a relay to attack systems that are not directly reachable from the attacker's network.

Plasma

Early Ethereum Layer 2 framework using child chains with fraud proofs on the parent.

Platform Engineering

Building internal developer platforms, golden paths, and self-service tooling so product teams ship faster with guardrails.

Port Scanning

Probing systems for open ports and services to identify potential entry points.

Post-Exploitation

Activities after initial access, including persistence, privilege escalation, credential access, and data collection.

Post-Quantum Cryptography

Also: quantum-safe cryptography

Algorithms designed to resist cryptanalysis by large-scale quantum computers.

Premine

Coins allocated to founders or investors before public mining or launch, disclosed in tokenomics.

Privacy Coin

Cryptocurrency designed to obscure sender, receiver, or amount by default.

Private Blockchain

Ledger operated among known participants, not open to the public.

Private Key

Secret number controlling a wallet; anyone with it can spend associated funds.

Privilege Escalation

Gaining higher-level permissions than originally granted, often from user to administrator or system.

Prompt Injection

Manipulating large language model inputs to bypass safeguards, leak data, or trigger unintended actions.

Proof of Authority (PoA)

Also: PoA

Consensus where approved validators produce blocks, common in private or consortium chains.

Proof of Burn

Consensus or distribution mechanism destroying coins to earn mining or staking rights.

Proof of Capacity

Mining by allocating disk space rather than compute, as in some altcoins.

Proof of History

Also: PoH

Solana's verifiable delay function ordering events before consensus for higher throughput.

Proof of Reserves

Exchange publishing cryptographic evidence that customer liabilities are backed by holdings.

Proof of Space and Time

Consensus using stored data proofs combined with verifiable delays.

Proof of Stake (PoS)

Also: PoS

A consensus model where validators stake locked coins to propose blocks and are penalized for dishonest behavior.

Proof of Work (PoW)

Also: PoW

A consensus model where miners expend computational work to add blocks, making rewriting history costly.

Proposer-Builder Separation

Also: PBS

Splitting block building from proposing to reduce validator MEV centralization.

Proto-Danksharding

Ethereum upgrade introducing blob data for cheaper Layer 2 data posting via EIP-4844.

Proxy Server

An intermediary that forwards client requests, enabling filtering, logging, anonymity, or inspection.

Public Blockchain

Open network where anyone can participate and verify transactions.

Public Key

Derived from the private key; shared to receive funds or verify signatures without spending power.

Public Key Infrastructure (PKI)

Also: PKI

The framework of policies, hardware, software, and procedures used to create, manage, distribute, and revoke digital certificates.

Pump and Dump

Coordinated hype to raise a token price followed by mass selling on retail buyers.

Purple Team

Collaboration between offensive and defensive teams to validate controls and improve detection using shared exercises.

QR Code Phishing (Quishing)

Also: quishing

Phishing that uses QR codes in email or physical media to steer victims to malicious sites, bypassing some link-scanner checks.

Quantitative Tightening (Token)

Reducing token emissions or burning supply to decrease inflation pressure.

QUIC

A UDP-based transport protocol that multiplexes streams with built-in encryption, forming the basis of HTTP/3.

Race Condition (Security)

Flaws where timing of operations allows bypass of checks, such as TOCTOU in file or permission handling.

Rainbow Table

Precomputed tables for reversing password hashes, mitigated by salting and slow hash functions.

Ransomware

Malware that encrypts victim data or locks systems and demands payment — often in cryptocurrency — in exchange for restoration.

Ransomware-as-a-Service (RaaS)

A criminal business model where operators lease ransomware infrastructure and kits to affiliates.

RBAC

Also: Role-Based Access Control

Role-Based Access Control — permissions assigned to roles rather than individuals, simplifying administration.

Real World Asset (RWA) Tokenization

Also: RWA

Representing physical or traditional financial assets as on-chain tokens for trading or settlement.

Rebase Token

Also: elastic supply

Token adjusting every holder's balance automatically to target a price or index.

Reconnaissance

Gathering information about targets before an attack, including open sources, scanning, and social profiling.

Recovery Phrase Security

Practices for offline backup, splitting, and never digitizing seed phrases.

Red Team

A group that simulates realistic adversaries to test detection, response, and resilience.

Reentrancy Attack

Exploit that calls back into a vulnerable contract before state updates finish, draining funds.

Relay Chain

Polkadot central chain providing shared security and message passing to parachains.

Remote Access Trojan (RAT)

Malware that provides remote control of a victim system, often including keylogging and file access.

Remote Browser Isolation

Running web browsing in an isolated environment so malicious content does not reach the endpoint.

Restaking

Using staked assets to secure additional protocols, adding reward and slashing risk.

Retrieval-Augmented Generation (RAG)

Also: RAG

Augmenting an LLM with retrieved documents from a knowledge base so answers are grounded in organization-specific data.

Reverse Engineering

Analyzing software or hardware to understand behavior, often used in malware analysis and vulnerability research.

Ring Signature

Signature hiding which member of a group signed, used in some privacy coins.

Risk Assessment

The process of identifying threats and vulnerabilities, estimating likelihood and impact, and prioritizing controls to reduce risk to an acceptable level.

Risk Management

Identifying, analyzing, and treating security risks in line with organizational appetite and regulations.

Rogue Access Point

An unauthorized Wi-Fi AP that lures users to connect for eavesdropping or credential capture.

Rollup

Also: optimistic rollup, ZK rollup

A Layer 2 approach that executes transactions off-chain and posts compressed proofs or data back to the base chain.

Rollup-as-a-Service

Also: RaaS L2

Hosted tooling to launch custom Layer 2 rollups without building from scratch.

Rootkit

Malware that hides its presence by manipulating the operating system or firmware.

RPC Endpoint

URL exposing blockchain JSON-RPC methods for wallets and dApps to read and submit transactions.

RSA

A widely used public-key algorithm for encryption and digital signatures, often with key lengths of 2048 bits or more.

Rug Pull

A scam where developers abandon a token or DeFi project after attracting investment, often draining liquidity or minting supply.

Rug Pull (Liquidity Removal)

Developers pulling LP tokens so traders cannot sell, a common DeFi scam.

Rug Pull Indicator

Red flags such as unlocked liquidity, anonymous team, or honeypot withdraw rules.

Runes (Bitcoin)

Bitcoin fungible token protocol using UTXO-based etching, alternative to BRC-20.

Runtime Application Self-Protection (RASP)

Security embedded in applications to detect and block attacks in real time during execution.

S/MIME

Secure/Multipurpose Internet Mail Extensions — standards for encrypting and signing email messages.

Salt (Cryptography)

Random data combined with passwords before hashing to ensure identical passwords produce different digests.

Same-Origin Policy

A browser rule restricting how documents from one origin can interact with resources from another.

Sandbox (Security)

An isolated environment for executing untrusted code to observe behavior without risking the host.

Sandwich Attack

MEV strategy placing buy and sell transactions around a victim swap to extract value.

Satoshi

Also: sats

Smallest unit of Bitcoin, one hundred millionth of a BTC (0.00000001 BTC).

SBOM

Software Bill of Materials — an inventory of components in software used to track vulnerabilities and supply chain risk.

SCADA Security

Protecting supervisory control and data acquisition systems used in utilities and manufacturing.

Schnorr Signature

Signature scheme enabling batch verification and used in Bitcoin Taproot.

Secrets Management

Secure storage, rotation, and access control for API keys, passwords, and certificates used by applications and pipelines.

Security Awareness Training

Education that helps employees recognize phishing, safe handling of data, and reporting suspicious activity.

Security Baseline

A documented minimum configuration standard for systems and applications to reduce avoidable risk.

Security Hardening

Reducing attack surface by disabling unnecessary services, applying secure configurations, and patching.

Security Information and Event Management (SIEM)

Also: SIEM

A platform that aggregates log and event data from across an environment to support detection, investigation, and compliance reporting.

Security Information Sharing

Exchange of threat indicators and context among organizations via ISACs or automated feeds.

Security Operations Center (SOC)

A team and facility that monitors, triages, and responds to security events around the clock.

Security Orchestration, Automation and Response (SOAR)

Platforms that automate playbook-driven incident workflows across tools and teams.

Security Posture

The overall strength of an organization's defenses, visibility, and readiness against threats.

Security Token

Token representing regulated financial assets such as equity or debt.

Seed Phrase

Also: recovery phrase, mnemonic phrase

A human-readable list of words that deterministically derives wallet private keys; must be stored offline and never shared.

SegWit

Bitcoin upgrade separating signature data to increase capacity and fix transaction malleability.

Selfish Mining

Strategy where miners withhold blocks to gain unfair advantage over honest miners.

Semi-Fungible Token

Token class where batches share IDs but individual serials may differ, often ERC-1155.

Separation of Duties

Dividing critical tasks among multiple people so no single individual can complete a sensitive transaction alone.

Sequencer

Entity ordering Layer 2 transactions before posting batches to the base chain.

Server-Side Request Forgery (SSRF)

Forcing a server to make requests to unintended destinations, often reaching internal services or cloud metadata.

Serverless Computing

Also: FaaS, functions as a service

Running code in managed, event-driven functions where the cloud provider scales capacity and billing is per invocation rather than per server.

Service Mesh

Infrastructure layer that handles service-to-service traffic with mutual TLS, retries, and telemetry, often via sidecar proxies.

Session Hijacking

Taking over a valid user session by stealing session tokens or cookies.

Session Management

How applications create, maintain, expire, and invalidate user sessions securely.

Shadow AI

Use of unapproved AI tools or models by employees, creating data leakage, compliance, and security risks outside IT governance.

Shadow IT

Use of hardware, software, or cloud services without approval, bypassing security governance.

Sharding

Splitting blockchain state or processing across parallel shards to improve scalability while preserving network security goals.

Sharding (Ethereum)

Planned scaling splitting Ethereum state across shard chains secured by the beacon chain.

Sharding Key

Data partition identifier in sharded database or blockchain designs.

Shimming

Inserting malicious code between legitimate components, such as payment card skimmers on readers.

Shoulder Surfing

Observing screens or keyboards to capture passwords, PINs, or confidential information.

Side-Channel Attack

Deriving secrets by measuring physical or timing properties such as power consumption or cache behavior.

Sidechain

Separate chain pegged to a parent chain, with its own validators and security tradeoffs.

Sign Message

Cryptographic proof of wallet control without broadcasting a transaction, used for login or auth.

Sign-In with Ethereum (SIWE)

Also: SIWE

Standard message format proving wallet control to log into apps without passwords.

SIM Swap Attack

Also: SIM swapping

Fraud where an attacker ports a victim's phone number to their SIM to intercept SMS-based MFA and account recovery codes.

Single Sign-On (SSO)

Also: SSO

Authentication scheme allowing one login to access multiple applications.

Skimming

Capturing card data from ATMs or point-of-sale devices using concealed hardware.

Slashing

Penalty destroying or locking a validator's stake for double-signing or prolonged downtime.

Slippage Tolerance

Maximum price movement a trader accepts when executing a DEX swap.

Smart Contract

Self-executing program logic on a blockchain that runs when defined conditions are met; bugs can cause irreversible financial loss.

Smart Contract Audit

Professional security review of contract code before mainnet deployment.

Smart Contract Wallet

Wallet implemented as on-chain code enabling multisig, recovery, and session keys.

Smishing

Phishing conducted via SMS text messages with malicious links or requests.

Snapshot (Governance)

Off-chain voting platform weighting votes by token balance at a block height.

SNMP Security

Securing network management protocol access with strong versions, communities, and ACLs to prevent reconnaissance.

SOC 2

AICPA trust service criteria audit report focused on security, availability, and confidentiality of service organizations.

SOC Metrics

Also: MTTD, MTTR

Measurements such as mean time to detect and respond used to evaluate security operations effectiveness.

Social Engineering

Psychological manipulation that tricks people into breaking security procedures — often the first step in larger attacks.

Social Recovery Wallet

Wallet where trusted guardians can help restore access without a seed phrase.

Soft Fork

Backward-compatible rule tightening where non-upgraded nodes still follow the same chain.

Software Composition Analysis (SCA)

Scanning applications for known vulnerabilities and license issues in open-source dependencies.

Software Supply Chain Security

Verifying integrity of code, dependencies, build pipelines, and distribution to prevent tampering.

Software-Defined Perimeter (SDP)

Architecture that hides infrastructure until devices and users authenticate, reducing exposed attack surface.

Solidity

Primary programming language for writing smart contracts on Ethereum and EVM chains.

Soulbound Token (SBT)

Also: SBT

Non-transferable token representing credentials, reputation, or identity.

Spam Transaction

Flooding a chain with low-value txs to congest the network or claim airdrops.

Spear Phishing

Targeted phishing aimed at specific individuals or roles using personalized messages.

SPL Token

Solana's standard for fungible and non-fungible tokens, similar in role to ERC-20/721.

Spot Market

Trading assets for immediate settlement rather than derivatives or margin.

SPV (Simplified Payment Verification)

Verifying transactions using block headers and Merkle proofs without a full node.

Spyware

Software that secretly monitors user activity, keystrokes, or communications.

SQL Injection

Also: SQLi

A code injection technique that exploits improper input handling to execute malicious SQL against a database, potentially exposing or modifying data.

Stablecoin

A cryptocurrency designed to track a fiat currency or other stable asset, using reserves, algorithms, or collateral.

Stablecoin Depeg

Also: depeg

When a stablecoin trades materially below or above its intended peg.

Stack Overflow

Overflowing a function's stack buffer in native code, a classic vector for control-flow hijacking.

Staking

Locking cryptocurrency to support network validation or DeFi protocols in return for rewards, with slashing or lockup risks.

Staking APR

Annualized rate of return from staking rewards before compounding effects.

Staking Derivatives

Financial products built on staked positions, including LSTs and restaking layers.

Staking Pool

Pooled capital delegating to validators with proportional reward distribution.

State Channel

Off-chain session updating balances with on-chain settlement only on dispute or close.

State Root

Merkle root committing to entire blockchain state in a block header.

State Trie

Also: Merkle Patricia trie

Merkle Patricia trie committing to all account balances and contract storage on EVM chains.

Steganography

Hiding data within other files such as images or audio to evade detection.

STRIDE

A threat modeling framework covering Spoofing, Tampering, Repudiation, Information disclosure, Denial of service, and Elevation of privilege.

Supply Chain Attack

Compromising software, hardware, or service providers to reach downstream customers.

Sybil Attack

One entity controlling many identities to influence voting, airdrops, or peer networks.

Symmetric Encryption

Encryption where the same secret key is used for both encryption and decryption.

Synthetic Asset

Also: synth

On-chain token tracking price of an external asset without direct custody of the underlying.

System Hardening

Applying secure configurations, updates, and minimal services to operating systems and appliances.

Tabletop Exercise

A discussion-based simulation where stakeholders walk through incident response roles and decisions.

Taproot

Bitcoin upgrade improving privacy and efficiency of certain transactions via Schnorr and Merkelized scripts.

Testnet

Non-production blockchain copy for development and testing with worthless tokens.

The Merge

Ethereum's 2022 transition from proof of work to proof of stake on the Beacon Chain.

Threat Actor

An individual or group with intent and capability to carry out malicious cyber activity.

Threat Hunting

Proactive searches through telemetry for hidden adversaries that automated alerts may miss.

Threat Intelligence

Also: CTI, cyber threat intelligence

Evidence-based knowledge about existing or emerging threats — including actors, tools, and campaigns — used to inform defensive decisions.

Threat Modeling

Structured analysis of how systems could be attacked to guide design and prioritization of mitigations.

Timelock

Contract constraint delaying execution until a future block or timestamp.

TLS

Also: SSL, Transport Layer Security

Transport Layer Security — a cryptographic protocol that secures communication over networks, widely used to protect HTTPS web traffic.

Token Bridge Liquidity

Pools or vaults funding cross-chain transfers on bridge protocols.

Token Curated Registry

Also: TCR

Economic game where depositors vote on list quality, slashing for bad entries.

Token Generation Event (TGE)

Moment tokens become transferable or tradable after sale or launch.

Token Lock

Time-bound contract preventing transfer of allocated tokens until unlock.

Token Standard

Also: ERC-20, ERC-721

A common smart contract interface for fungible or non-fungible tokens on a platform, such as ERC-20 or ERC-721 on Ethereum.

Token Vesting

Gradual release of allocated tokens to team or investors over a schedule.

Tokenization

Replacing sensitive data with non-sensitive tokens that map back through a secure vault.

Tokenomics

Economic design of a token: supply, distribution, emissions, utility, and incentives.

Total Value Locked (TVL)

Also: TVL

Sum of assets deposited in a DeFi protocol or chain, used as a size metric.

Transaction Finality

Confidence that a transaction will not be reversed; varies by chain and confirmation count.

Transaction Index

Position of a transaction within a block, paired with block hash for unique ID.

Transaction Receipt

Record of execution outcome, gas used, logs, and status for a mined transaction.

Transformer

Also: Transformer model

A neural network architecture using self-attention that underpins most modern LLMs and many vision and speech models.

Travel Rule (Crypto)

Requirement for VASPs to share originator and beneficiary data on transfers above thresholds.

Trojan Horse

Malware disguised as legitimate software that users install willingly.

Trustless

Interaction secured by cryptography and consensus rather than faith in a central party.

Typosquatting

Registering domains similar to popular brands to catch mistyped URLs for phishing or malware.

Uniswap-Style AMM

DEX using constant product pools popularized by Uniswap and many forks.

User and Entity Behavior Analytics (UEBA)

Analytics that baseline user and machine behavior to detect anomalies indicating compromise.

User Operation

Also: UserOp

ERC-4337 pseudo-transaction describing actions an abstract account wants to perform.

Utility Token

Token granting access to a product, service, or network feature rather than equity.

UTXO

Also: unspent transaction output

Unspent transaction output model used by Bitcoin: coins are tracked as outputs consumed by new transactions.

Validator

A network participant in proof-of-stake systems that proposes or attests blocks and earns rewards for honest operation.

Validator Client

Software implementing proof-of-stake duties such as proposing and attesting blocks.

Validator Node

Server running client software participating in block production or attestation.

Validator Set

The group of nodes authorized or elected to produce blocks in a proof-of-stake network.

Validity Proof

Cryptographic proof that off-chain computation was executed correctly, used in ZK rollups.

Validium

Layer 2 using off-chain data availability with on-chain validity proofs.

Vanity Address

Blockchain address with chosen prefix or pattern, generated by grinding keys.

Vector Database

Also: vector store

A database optimized for storing embeddings and fast similarity search, commonly used in RAG and recommendation systems.

Vesting Cliff

Initial period before any vested tokens unlock for recipients.

VLAN

Virtual LAN — logical network segmentation at Layer 2, misconfiguration of which can enable hopping attacks.

VLAN Hopping

Exploiting switch misconfigurations to access traffic on VLANs a host should not reach.

VM Escape

Breaking out of a virtual machine to execute code on the underlying hypervisor or host.

Volatility (Crypto)

Large short-term price swings common in cryptocurrency markets.

VPN

Also: Virtual Private Network

Virtual Private Network — technology that creates an encrypted tunnel between a device and a network, protecting traffic from interception on untrusted links.

Vulnerability

Also: vuln

A weakness in a system, application, or process that could be exploited by a threat to compromise confidentiality, integrity, or availability.

Vulnerability Assessment

Systematic identification and rating of weaknesses, often using scanning tools and manual review.

Vulnerability Management

Continuous process of discovering, prioritizing, remediating, and verifying fixes for vulnerabilities.

WAF

Also: Web Application Firewall

Web Application Firewall — filters HTTP traffic to block common web attacks such as SQLi and XSS.

Wallet Address

Also: crypto address

A public identifier derived from keys, used to receive cryptocurrency on a given blockchain.

Wallet Connect

Also: WalletConnect

Open protocol linking mobile wallets to desktop dApps via QR or deep links.

Wardriving

Searching for wireless networks by driving or walking with scanning equipment.

Watch-Only Wallet

Wallet tracking addresses without private keys, for monitoring only.

Watering Hole Attack

Compromising websites frequented by a target group to infect visitors with malware.

Web3

A vision of the web built around decentralized protocols, wallets, and token-based ownership rather than centralized platforms alone.

Web3 Provider

JavaScript interface such as window.ethereum injected by wallets for dApp communication.

WebAssembly (Wasm)

Also: Wasm

A portable binary instruction format that runs near-native code in browsers and other runtimes with a strong sandbox.

Webhook

An HTTP callback where one system notifies another when an event occurs, instead of the receiver polling repeatedly.

Whale (Crypto)

Holder of very large token balances able to move markets with trades.

Whaling

Phishing targeting senior executives or high-value individuals.

White Hat

Security professionals who test and improve defenses with authorization and ethical standards.

Whitelist (Token Sale)

Approved addresses allowed to mint or buy before public sale.

Whitepaper

Document describing a project's technology, tokenomics, and roadmap.

Wi-Fi Protected Access 3 (WPA3)

The latest Wi-Fi security protocol offering stronger encryption and protection against offline password guessing.

Worm

Self-replicating malware that spreads across networks without requiring user action.

Wrapped Bitcoin (WBTC)

Also: WBTC

ERC-20 token backed by custodied Bitcoin, bringing BTC liquidity to Ethereum DeFi.

Wrapped Ether (WETH)

Also: WETH

ERC-20 wrapped form of ETH used as a standard token in DeFi protocols.

Wrapped Token

On-chain representation of an asset from another chain or system, backed or pegged.

x402 Payments

HTTP 402-based micropayment pattern for paying APIs with stablecoins or crypto.

XML External Entity (XXE)

Exploiting weak XML parser configuration to read files, perform SSRF, or cause denial of service.

YARA

A pattern-matching language for identifying and classifying malware samples based on textual or binary rules.

Yield Aggregator

Also: vault aggregator

Protocol auto-compounding deposits across multiple DeFi strategies.

Yield Farming

Also: farming

Moving capital across DeFi protocols to maximize token rewards and fee income.

Zero Day

Also: 0-day, zero-day exploit

A vulnerability that is unknown to the vendor or public and for which no patch is yet available, giving defenders zero days to prepare before exploitation may occur.

Zero Trust

Also: zero trust architecture, ZTA

A security model that assumes no implicit trust based on network location — every access request must be authenticated, authorized, and continuously validated.

Zero Trust Network Access (ZTNA)

Brokered access to applications based on identity and context rather than implicit network trust.

Zero-Confirmation Transaction

Also: 0-conf

Accepting payment before any block confirmation, risky due to double spends.

Zero-Knowledge Proof (ZKP)

Also: ZKP

Proof that a statement is true without revealing the underlying secret data.

ZK Rollup

Also: zero-knowledge rollup

Layer 2 posting validity proofs to the base chain, offering faster finality than optimistic designs.

zk-SNARK

Compact zero-knowledge proof with a trusted setup, used in privacy and scaling systems.

zk-STARK

Scalable transparent zero-knowledge proof without trusted setup, larger proofs than SNARKs.