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, thanks to reporting by Bloomberg.The hacking group got into more than 400 laptop and desktop computers, many of which were linked to senior leaders focused on sanctions, international affairs and intelligence. They also accessed employee usernames and passwords, in addition to more than 3,000 files on unclassified personal computers. These documents included travel data, organizational charts, sanction materials and foreign investment metrics.An agency report indicates that the perpetrators likely stole a whole lot of this data, but were unable to get into the Treasurys classified or email systems. Subsequent reporting, also from Bloomberg, indicates around 50 classified files were stolen from the computer of Treasury Secretary Janet Yellen. The hackers also accessed materials regarding investigations run by the Committee on Foreign Investment. This committee reviews security implications surrounding real estate purchases and foreign investments in the US.The agency report also notes that there wasnt any evidence to suggest that the hackers tried to hide in the Treasurys systems for the purpose of long-term intelligence gathering, and they didnt leave behind any malware.China reacts on Treasury-Hack pic.twitter.com/7j7OaQ6eKD Willem Middelkoop (@wmiddelkoop) January 2, 2025 Investigators have attributed the intrusion to a notorious Chinese state-sponsored hacking group called Silk Typhoon, Halfnium or UNC5221. It has been suggested that they performed the hack outside of normal working hours to avoid detection. Last month, a spokesperson for the Chinese Foreign Ministry called the accusation that the attack was state-sponsored unwarranted and groundless.Counterintelligence officials are still in the midst of a comprehensive damage assessment but Treasury employees are set to brief the Senate Committee on Banking, Housing and Urban Affairs on the matter this week.Update, January 17 2025, 10:47AM ET: This story has been updated to include additional reporting.This article originally appeared on Engadget at https://www.engadget.com/cybersecurity/china-linked-hackers-accessed-over-400-us-treasury-computers-182420268.html?src=rss