What Is a “51% Attack” and Why Is Hash Rate Relevant to It?

A 51% attack is a theoretical scenario where a single entity or group gains control of more than 50% of a Proof-of-Work blockchain's total hash rate. With this majority control, the attacker could effectively block new transactions, reverse recent transactions (double-spending), and prevent other miners from finding blocks.

Hash rate is relevant because the higher the network's total hash rate, the more computational power and resources are required to amass the 51% majority, making the attack prohibitively expensive and unlikely.