A 51% attack is the reorganization of a blockchain by malevolent actors who control more than 51% of the total hashing or validating the power of a coin. Rather than how many bitcoins are held, a 51% attack focuses on who controls the mining process. Mining networks protected by ASICs are speedier and less prone to attack than those that use GPUs. It is potentially conceivable to execute a 51% attack using only rented hash power using cloud services like NiceHash, which calls itself a “hash-power broker,”, especially against smaller, GPU-only networks.