Blockchain Glossary

51% Attack

August 28th, 2020   |   Updated on August 28th, 2021

Attackers use 51% attacks to reverse transactions that have already taken place, in a blockchain, in what has come to be known as double spend. For instance, one can spend 5 bitcoins to purchase a motorcycle.

Once the bike is delivered, logic dictates that Bitcoins are to be transferred to cater for the cost of the bike and can activate the attack.

However, on performing a 51% attack, an attacker would be able to reverse a transaction resulting in all coins used to fund the transaction being refunded.

In the end, the attacker will be the owner of the motorcycle as well as the bitcoins used to buy it.