The recent 51% attack occurs when somebody controls the majority of mining power on a PoW [Proof-of-Work] blockchain network. This implies that the majority block verifier can forestall other users from mining, thereby reversing transactions.
While several have assumed that a 51% attack would be followed with malicious intent, this recent case happened as the 2 mining pools tried to forestall an unidentified party from taking some coins that – due to a ‘code update‘ – were essentially “up for grabs.”
As per Swann, 2 miners with majority management of the network – BTC.top & BTC.com – performed the attack in an attempt to prevent an unknown miner from taking coins that were transferred to an “anyone can spend” address following the genuine hard-fork earlier in May 2017. As per Swann’s tweets:
“When an unknown miner tried to take the coins themselves, http://BTC.TOP & http://BTC.COM saw and quickly decided to re-org these transactions, in favor of their own transactions, paying the same P2SH coins, + several others … thereby just 2 miners, on the secret & w/ no hassle, took it upon themselves to get rid of the 2 blocks w/ another’s Transactions, & replaced it with their own.”
51% attack’ have usually been considered as an undesirable and unprofitable choice to take funds, as it would require an enormous amount of computing power, and once a network is compromised, users would would ostensibly flee.
As ‘reported‘ earlier, the Ethereum Classic [ETC] ‘blockchain‘ underwent a 51% attack earlier in January. Researchers at the crypto exchange Gate.io reportedly found that a hacker had reversed four transactions, leading to a loss of around 4,200 ETC. The exchange ensured to compensate the affected users, and requested other trading platforms to immediately block transactions initiated by the attacker’s address.