The hacker behind China infiltrates the U.S. Treasury Department's computer network... a "critical security case."

A hacker suspected of having the Chinese government behind him recently infiltrated the U.S. Treasury Department's computer network and stole some information.

The U.S. government has called the incident a "major cybersecurity incident" and launched an investigation involving a number of investigative agencies.

According to CNN and AFP, hackers accessed unsecured documents remotely to some working computers in the Treasury Department on the 2nd.

The hacker hacked Beyond Trust, a company that provides cybersecurity services to the Treasury Department, then seized digital keys and passed through the Treasury Department's computer security system.

The Treasury Department said there were multiple computers accessed by hackers, but did not disclose the exact extent of the damage.

The Treasury Department reported the incident to the U.S. Senate Banking Committee and said it believes it was the work of an APT, intelligent persistent hacking agent sponsored by the Chinese government, based on various circumstances.

APT refers to a hacking method that targets a specific organization rather than an unspecified number of people and continues to attack by using various means.

Such APT attacks are considered "significant cybersecurity incidents," the Treasury Department said in a report.

Shortly after receiving a report from Beyond Trust on the situation on the 8th, the Treasury Department is working with law enforcement authorities to inform the Cyber Infrastructure Security Agency (CISA) under the Department of Homeland Security and to identify the characteristics of the incident and the damage.

In addition to CISA, the FBI, intelligence agencies and private forensics companies are jointly participating in the investigation, the Treasury Department said.