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51% Attack

51% Attack

Last Updated: January 23, 2026

51% Attack is a blockchain takeover where a group controls over half of the network's mining power, risking transaction manipulation.

51% Attack is a potential vulnerability in blockchain networks. It occurs when a single entity or group gains control of more than 50% of the network's mining power or computational capability. This majority control allows the attacker to manipulate the blockchain by altering transaction records, double-spending coins, or preventing new transactions from being confirmed. While theoretically possible, executing such an attack requires significant resources. It undermines the network's integrity and trustworthiness, posing a serious threat to decentralized systems.