# 51% Attack

*Crypto & Digital Assets — Finicade finance glossary*

A 51% attack is one party controlling most of a network's mining power or stake, allowing them to reverse recent transactions and double-spend. It cannot rewrite deep history or steal from arbitrary addresses. Large chains are effectively immune on cost grounds, while smaller proof-of-work chains have been attacked repeatedly — the security budget scales with the value being secured, and so does the attack cost.

**Also known as:** 51 percent attack, majority attack, double spend attack

**Related terms:** [Proof of Work](https://finicade.com/glossary/proof-of-work), [Consensus Mechanism](https://finicade.com/glossary/consensus-mechanism), [Mining](https://finicade.com/glossary/mining), [Blockchain](https://finicade.com/glossary/blockchain), [Proof of Stake](https://finicade.com/glossary/proof-of-stake)

Source: https://finicade.com/glossary/51-percent-attack