51% attack

A 51% attack occurs when a single entity gains control of over half of a blockchain's computing power (hash rate). This majority control allows them to manipulate the network by double-spending coins, preventing new transactions from being confirmed, or rewriting transaction history. Essentially, with majority control, they can undermine the integrity and trustworthiness of the blockchain, potentially causing financial loss for other users. While technically challenging and costly to execute on large networks like Bitcoin, smaller networks are more vulnerable to such attacks.