Breach at security contractor USIS went undetected for months; similar to prior China hackings

A cyberattack similar to previous hacker intrusions from China penetrated computer networks for months at the government's leading security clearance contractor before the company noticed the break-in. That's according to officials and others familiar with an FBI investigation and related inquiries.

The breach compromised the records of at least 25,000 employees at the Homeland Security Department.

There are concerns about why computer alarms inside the company — USIS — failed to quickly detect the hackers and whether federal agencies should have monitored the firm's practices more closely. The officials spoke only on condition of anonymity because they were not authorized to talk publicly about a continuing criminal investigation.

A USIS report says the company's computer security was reviewed and approved by the government.