( CNN ) -- USIS , a major contractor providing background checks for the U.S. government , said Wednesday that hackers suspected to be working for a foreign government breached its computer systems . Government officials said the attackers might have stolen information belonging to U.S. government employees . The FBI is investigating , and the Department of Homeland Security said it has halted providing employee data to USIS for background checks until it can be assured the data wo n't be compromised . The company said in a statement that experts investigating the breach `` believe it has all the markings of a state-sponsored attack . '' DHS spokesman Peter Boogaard said , `` 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 . '' New leaker disclosing U.S. secrets , government concludes . DHS warned employees to be on guard for unsolicited requests for private and financial information . USIS has been a beleaguered company of sorts in the past year . The Justice Department has joined a lawsuit accusing the company of shoddy background check work and defrauding the government . It conducted background checks on NSA leaker Edward Snowden and Aaron Alexis , who carried out the Washington Navy Yard mass shooting . Government officials have said the Alexis background check met government procedures and that there are no indications the Snowden check was deficient . USIS said it uncovered the breach recently and reported it to authorities . The company is working with the Office of Personnel Management and the DHS US-Cert cyber-response teams to investigate and mitigate the breach . Opinion : Cybercrime is big money for hackers . Report : Hackers in Iran use social media to target senior U.S. , Israeli officials . DHS : Hackers infiltrate public utility .
It is a major contractor performing background checks for the U.S. government . It said hackers breached its computer system ; FBI is investigating . It said experts ` ` believe it has all the markings of a state - sponsored attack '' Department of Homeland Security has halted providing employee data to USIS .