The cryptocurrency industry is under threat from a lot of different angles. One of the biggest potential problems is to so‐called 51% attack, which can disrupt networks in very quick succession. The year 2018 has been quite successful in this regard, as no less than seven 51% attacks have been performed successfully. The following incidents are ranked from oldest to most recent.The 51% attack spree of 2018 kicked off with a successful attack against Electroneum in April of 2018. This smaller altcoin was based on the CryptoNight algorithm, although the developers have made some changed in this regard ever since. A successful 51% attack affected the network for a little while, but Electroneum eventually recovered and moved on.