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Web3 security glossary

Short, plain-language definitions of the terms you will meet in a smart-contract audit.

Core terms

TermMeaning
ReentrancyRe-entering a function via an external call before its state is updated, enabling repeated withdrawals.
MEVMaximal Extractable Value: profit a block producer or searcher can extract by reordering, inserting or censoring transactions.
Sandwich attackAn MEV tactic that places one transaction before and one after a victim's trade to profit from the induced price movement.
TWAPTime-Weighted Average Price: an oracle method resistant to single-block price manipulation.
Flash loanAn uncollateralized loan repaid within the same transaction, often used to amplify manipulation.
delegatecallA call that runs another contract's code in the caller's storage context; dangerous if the target is untrusted.
Checks-Effects-InteractionsA pattern: validate inputs, update state, then interact with external contracts.
PDAProgram Derived Address on Solana; must be validated with the correct seeds and bump.
Signer checkOn Solana, verifying an account actually signed the transaction before trusting it.
SWCSmart Contract Weakness Classification, a registry of known weakness types.

OSINT & tooling terms

TermMeaning
OSINTOpen-Source Intelligence: gathering data from publicly available sources.
WHOISProtocol for querying domain/IP registration records (registrar, dates, owner).
RDAPRegistration Data Access Protocol: the modern, JSON-based successor to WHOIS.
DNS / DoHDomain Name System; DoH resolves DNS over encrypted HTTPS.
CVECommon Vulnerabilities and Exposures: a public ID for a known security flaw.
ASNAutonomous System Number: identifies a network on the internet (e.g. an ISP).
BGPBorder Gateway Protocol: how networks announce routes/prefixes between each other.
Reverse DNS (PTR)Maps an IP address back to a hostname via a PTR record.
AES-256 / PBKDF2Strong symmetric cipher; PBKDF2 derives a key from a password with many iterations.
Shodan InternetDBFree passive index of open ports, tags and CVEs observed for an IP.
EONET / USGSNASA natural-event feed and US Geological Survey earthquake feed (real-time).

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