Chinese state-sponsored hackers breached the US Treasury Department, accessing unclassified files on computers of top officials including Secretary Janet Yellen. Over 400 devices were compromised using a third-party software vendor's security flaws.

The hackers reportedly breached more than 400 computers and 3,000 files on personal devices. Despite the scale of the breach, classified government systems were not penetrated, a critical aspect that has helped limit the potential fallout of the cyberattack.

The US Treasury Department announced in a letter back in December that it had been the victim of a security breach, attributing it to a “China state-sponsored Advanced Persistent Threat actor.” Now we know more about the extent of the hack,