In possibly the largest known cryptocurrency hack to date, Japanese exchange Coincheck announced Friday that they had lost 58 billion yen, approximately $530 billion, worth of XEM cryptocurrency. This surpasses the 48 billion yen worth of Bitcoin lost by the Mt. Gox Bitcoin exchange in 2014.
XEM (or NEM coins), created by the Singapore-based NEM Foundation, is one of the most popular cryptocurrencies in the world, according to Reuters. Coincheck acknowledged its security practices on XEM were insufficient, however. As Money reports:
Coincheck said it used different security standards for different currencies, and that unlike customers' Bitcoin holdings, their XEM funds were stored in a "hot wallet" online instead of a "cold wallet" offline—a scenario ripe for hackers.
The company also failed to use multi-signature authentication on XEM funds, which would require at least two people for access.
Although blockchain technology has enabled Coincheck to identify the 11 addresses where the stolen coins ended up, and set up a tool for exchanges to automatically reject purchases made with them, hackers may still be able to use the funds via "tumblers" - exchanges that act like cryptocurrency laundering services. Coincheck has promised to reimburse 90 percent of the losses.
Read more about the incident here.