Tokyo-based cryptocurrency exchange Coincheck just made history, and not in a good way. It has lost around $534 million worth of NEM tokens, one of the lesser-known cryptocurrencies, after its network was hacked on January 25th, 12:57pm EST. The attackers remained undetected for eight hours, giving them enough time to steal 523 million tokens kept in a "hot wallet," a type of storage that's connected to the internet for easy spending. While the exact value of the stolen coins are unclear due to the ever-changing nature of cryptocurrency -- it's $400 million at the very least -- Coincheck might have already lost more than what Mt. Gox did a few years ago.