When Ileana Privetera started working for the contractor USIS, the firm that vetted National Security Agency leaker Edward Snowden and Washington Navy Yard shooter Aaron Alexis, it sounded like the perfect job. A mother, she would have flexible hours for her family, and she would be helping the country by running background checks on people who were doing the government's most critical jobs.

She quickly learned that she was being asked to do the impossible.

A computer-software system spat out assignments for her every week with new people to interview. The deadlines were merciless, with as many as 10 cases due in a single day.