# Security Content type: Topic Hub Summary: Blockchain security threats, vulnerabilities, and protections Related resources: - 51% Attack (Glossary Term): https://theblockchainlibrary.com/glossary/51-attack - Address Poisoning (Glossary Term): https://theblockchainlibrary.com/glossary/address-poisoning - Audit (Glossary Term): https://theblockchainlibrary.com/glossary/audit - Bridge Exploit (Glossary Term): https://theblockchainlibrary.com/glossary/bridge-exploit - Bug Bounty (Glossary Term): https://theblockchainlibrary.com/glossary/bug-bounty
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Security

Blockchain security threats, vulnerabilities, and protections

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12 Glossary Terms
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Key Glossary Terms

Essential vocabulary for this topic

51% Attack

intermediate

An attack where one entity or coalition controls enough consensus power to reorganize blocks, censor transactions, or attempt double spending.

Address Poisoning

intermediate

A scam where attackers create lookalike address activity so victims may accidentally send funds to the wrong address.

Audit

beginner

A smart contract audit is a comprehensive, systematic examination of a blockchain project's source code by independent security experts. The goal is to identify vulnerabilities, logical errors, and potential security flaws that could lead to exploits or financial loss. Auditors review the code for compliance with best practices, test for edge cases, and analyze the interaction between different smart contracts to ensure the protocol functions as intended before it is deployed on a mainnet.

Security

Bridge Exploit

advanced

An attack that compromises a cross-chain bridge's contracts, validators, keys, proofs, or custody mechanisms.

Bug Bounty

beginner

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

Double Signing

advanced

A proof-of-stake violation where a validator signs conflicting blocks or votes for the same consensus height or slot.