A 51% attack is an attack on a blockchain network where an attacker gains control of more than 50% of the network’s computing power or hash rate. This allows them to prevent new transactions from being confirmed, double-spend coins, and stop other miners from being rewarded.
The purpose of a 51% attack is to gain control of the blockchain and perform malicious activities that would not be possible with a smaller proportion of the network’s computing power. This could include double-spending coins, changing the record of past transactions, or preventing other users from completing valid transactions.
The threat of a 51% attack is one of the main challenges for blockchain networks. As decentralized networks rely on consensus for security and trust, if an attacker controls more than 50% of the network’s hashrate, they can effectively manipulate the network and disrupt its security and functionality.
A 51% attack usually requires an attacker to acquire a large amount of computing power and resources to overpower the network. As mining new coins can be very expensive, an attacker’s goal is usually to double-spend coins that have already been spent, preventing them from reaching their intended recipient.
Fortunately, due to the distributed nature of most blockchain protocols, it is extremely difficult to perform a 51% attack. As the computing power of the network grows, it becomes increasingly expensive to acquire enough hashrate to overpower the network.