According to his prepared testimony, 18 government employees have already been convicted of falsifying the background checks they had been hired to conduct. That's despite the OPM's claim that it doesn't have the proper funding to oversee the background check process.

The clearance system — which has vetted some 5 million Americans for access to classified material, according to the Director of National Intelligence — has come under new scrutiny since the revelation of top-secret National Security Agency surveillance programs by 29-year-old defense contractor Edward Snowden. Snowden, until recently an employee of Booz Allen Hamilton, held a top-secret clearance despite never graduating high school.

McFarland will testify before a joint hearing of Senate subcommittees on homeland security.