Reuters sources say that the hackers exploited a floor and software made by solar winds to target a federal payroll agency.

Solar winds is the company that alleged Russian hackers used to preach US government networks and private firms last year.

That attack only came to light in December, but hackers are believed to have breached the networks for months.

U.

S lawmakers have called the alleged Russian hack a national security emergency, but this latest breach by suspected Chinese hackers marks a new twist in the saga.

The Chinese hackers are believed to have exploited a different floor in the software of solar winds to the Russian hackers, according to sources.

FBI investigators recently found that the National Finance Center was affected by the breach.

It's responsible for handling the payroll of several federal agencies, including the Department of Homeland Security.

Reuters was not able to establish how many organizations were affected by the suspected Chinese operation, but there are now fears that data on thousands of government employees may have been compromised.

The FBI declined to comment.

China's Foreign Ministry said any allegations should be supported with evidence.

Reuters sources say that to espionage efforts were separate and distinctly different operations.

But both show how hackers are now focusing on weaknesses in obscure but essential software products that are widely used by major corporations and government agencies.