Cryptocurrency firms and investigators are racing to freeze and track down billions of dollars of stolen digital cash following what appears to be the largest crypto heist of all time. On Thursday, starting at around 4pm ET, hackers started quickly siphoning around $6.3 billion in cryptocurrencies, spread across multiple blockchains, from wallets belonging to crypto exchange Binance .

Following the theft, Binance almost immediately suspended all deposits and withdrawals from its services as part of its investigation into the hack and says it is working to identify who was behind the breach. The company, along with other crypto firms, says it has so far been able to freeze around half of the stolen funds—essentially stopping hackers moving the money further or trying to cash it out. Much of the remaining crypto may not be possible to freeze, however.

Three crypto tracing firms have been quick to link the attack potentially to North Korean hackers.…