April 4, 2019
Ethereum Classic is the latest cryptocurrency that has been stolen in an online heist, as reported by Ars Technica. In what is known as a “rollback attack”, almost $500,000 worth of the digital coin was stolen when hackers rewrote blockchain, allowing the thieves to recover previously spent coins to re-spend.
Rollback attacks are also known as “51% attacks” because this method of stealing digital currency is theoretically only possible when the thief controls a majority of the central processing unit that is generating the coin’s blockchain. If a user has control of more than half of the network's computing power, they can modify blockchain records and reverse previous transactions. For this reason, the more users there are maintaining a blockchain, the less vulnerable it is to theft.
In 2018, over $1 billion worth of cryptocurrency was stolen from cryptocurrency exchanges. Thefts are the result of individuals or governments exploiting weaknesses in cryptocurrency software. They also happen through hacking passwords and other personal information.
Authors: Jaclyn Tilak and Ti-Anna Wang