Binance says the $6.34 billion heist ran through a rigged coding test and an internal AI tool the attackers used to take over two more engineers' computers

Binance has published its first incident report on last week's theft, the biggest sum ever targeted in a crypto heist: about $6.34 billion. Roughly $2.85 billion has been frozen or intercepted. The FBI has blamed North Korea's TraderTraitor group; North Korea rejects that.

What happened

Binance says it was a months-long campaign, not a single phishing click. In June, a wallet engineer downloaded a tampered Homebrew installer while searching for a popular AI coding tool. Security caught it and swapped his device, but the attackers had already learned what he did and who he worked with.

In September, a second engineer was approached on a real job-hunting platform by a fake project director. After two interviews with a fake HR person and a fake CEO, he was asked to download a coding 'assignment' onto his work computer. Setting it up ran hidden malware that swapped in a rogue copy of a developer tool component and phoned home. Binance says its endpoint protection didn't detect it.

Where the AI tool came in

On 20 October, the attackers used that infected machine and an internal AI tool to take control of two more engineers' computers, including the first engineer's new one. Binance hasn't explained how the AI tool was used. That first engineer's machine held a token allowing container deployments.

On 29 October, the attackers logged in to the third engineer's computer, deployed a container with the stolen credential and started a script that moved funds out through an internal wallet signing service, outside the normal withdrawal process. Hot wallets sent about 970,500 SOL, 44.2 million OP and 18,270 BTC to attacker addresses. They also used the signing service to abuse an Ethereum feature called EIP-7702, giving their own smart contract partial control of a hot wallet. That kept money moving even after Binance suspended withdrawals, and because the wallet used multi-party computation, there was no single key to revoke it quickly.

What Binance did

Binance apologised, saying it should not have happened. It says it has rebuilt the affected wallet system and the AI tool, replaced devices, retired the engineers' credentials and tokens, and brought in independent security firms. It says it has set aside funds to cover the loss, and withdrawals have broadly resumed.

Lesson for builders

An internal AI tool that can act on colleagues' machines is a highway between teams. If one infected laptop can drive it, so can an attacker. Give internal agents the narrowest reach possible, require a second person to approve anything that touches another device or a signing service, and log every action they take outside the agent itself.