The Falls Church, Virginia-based US Investigations Services, which provides background checks for the Department of Homeland Security, announced Wednesday it was the victim of a cyber attack. “It has all the markings of a state-sponsored attack,” it said in a statement. As a result, DHS has stopped all work with the company pending a multi-agency investigation. “At this time, our forensic analysis has concluded that some DHS personnel may have been affected, and DHS has notified its entire workforce, out of an abundance of caution, to advise them to monitor their financial accounts for suspicious activity,” a spokesman for the agency said. USIS is the largest private provider of background checks for the federal government.