The Treasury notified the Senate Banking Committee of the breach in a letter viewed by several media outlets. It called the breach a “major incident”. Department policy categorises nation state hacking incidents as “major”, according to the letter.
The department didn’t say how many workstations had been accessed or what kind of documents the hackers could have obtained. But in its letter to lawmakers, the department said “at this time there is no evidence indicating the threat actor has continued access to Treasury information”.