Cryptos are considered safe and still hackers are known to commit thefts amounting to a few billion dollars every years. Chainanalysis, a blockchain analytics platform, points out such thefts. Most of the thefts occur over DeFi protocols. Some currency is stole through cross-chain bridges protocol. This protocol relates to the porting of cryptos from one blockchain to another. The assets of the users are locked into a smart contract on the original chain. The equivalent assets are minted on the second chain. At times, the bridge expands. Any error in underlying smart contact code or other weak spot when detected could be exploited by the hackers.

Many such hackers originate from North Korea. These hackers send large sums to mixers. They use Tornado Cash to launder cryptos. Sinbad is a custodial mixer of Bitcoin. North Korean hackers send Bitcoin worth millions of dollars to the mixer.