The hack initially took advantage of a vulnerability in the Poly network, a platform that connects different blockchains so that they can work together. The hackers then made off with $600 million worth of cryptocurrency, but just when it was thought all was lost, they returned almost half of it.
According to Poly, they received a message from the hackers that was embedded in a cryptocurrency transaction that said that they were “ready to return” the funds. To date, about $258 million has been returned, but it is unclear what will happen to the remainder.
While it is unclear what the motives are behind the return, some speculate that the difficulty in offloading the cryptocurrency could be the reason why.
Speaking to CNBC in an email, Tom Robinson, chief scientist of blockchain analytics firm Elliptic said, “I think this demonstrates that even if you can steal cryptoassets, laundering them and cashing out is extremely difficult, due to the transparency of the blockchain and the use of blockchain analytics. In this case the hacker concluded that the safest option was just to return the stolen assets.”