Chinese state-sponsored hackers breached the Treasury Department's computer security guardrails this month, according to a letter to lawmakers that Treasury officials provided to Reuters.

The "threat actor" was able to access the workstations via a compromised third-party cybersecurity service provider called BeyondTrust, the department said.

Chinese state-sponsored hackers infiltrated the U.S. Treasury Department by exploiting a vulnerability in third-party software provider BeyondTrust, granting them remote access to several workstations and unclassified documents.