A fraudulent SSN may be indicative of identity theft, incorrect claims of citizenship status, or concealment of a "past life". Background screening firms usually perform a Social Security trace to determine where the applicant or employee has lived. The hiring of undocumented workers has become an increasing issue for American businesses since the formation of the Department of Homeland Security and its Immigration and Customs Enforcement (ICE) division, as immigration raids have forced employers to consider including legal working status as part of their background screening process.[citation needed] All employers are required to keep government Form I-9 documents on all employees and some states mandate the use of the federal E-Verify program to research the working status of Social Security numbers.