A company that performs background checks for the US Department of Homeland Security has been hacked.

US Investigations Services (USIS) had all the personal information about DHS employees and it is likely that the network was hacked by a foreign power. DHS has stopped working with the company and a "multi-agency cyber response team is working out what happened.

DHS spokesman Peter Boogaard said Homeland Security forensic experts had worked out that some DHS personnel may have been affected but has warned all of them just in case. 

Security experts believe it has all the fingerprints of a state-sponsored attack. After all a foreign power would love to know who Homeland Security’s agents are. USIS is a big commercial provider of background investigations to the federal government, has over 5,700 employees and provides its services all over the world.