The agency last month issued a scathing report alleging a six-year accounting fraud at Fannie Mae, the largest U.S. buyer and guarantor of home mortgages. It said employees manipulated accounting to hit company quarterly earnings targets so senior executives could pocket hundreds of millions in bonuses from 1998 to 2004. "The first line of defense is that the board of Fannie Mae should go after these individuals and try to get restitution" of some of the bonus money, Lockhart testified.