51% Attack

A 51% attack occurs when a single entity gains control of over half of a blockchain network’s mining power or validation authority. This majority control allows the attacker to manipulate the blockchain by reversing transactions, double-spending coins, or halting new transactions. While rare in large blockchains like Bitcoin or Ethereum, smaller or newer blockchains with less distributed mining power are more vulnerable. Such attacks threaten the core trust and immutability of decentralized networks. Preventing 51% attacks involves promoting decentralization, encouraging more nodes, and implementing advanced consensus mechanisms like proof-of-stake or hybrid models.