North Korea is behind the massive crypto hack, according to several blockchain monitoring firms and a well-known researcher

The Singapore-based crypto exchange Bybit is offering a large bounty for information that could lead to the recovery of the funds that were stolen in a major hack.

Cryptocurrency exchange Bybit said last week hackers had stolen digital tokens worth around $1.5 billion, in what researchers called the biggest crypto heist of all time. Bybit CEO Ben Zhou said the crypto was taken from a "cold wallet" - a digital wallet usually stored offline and so supposedly more secure - that was used for ether tokens.