The government has accused its largest security background check contractor of defrauding the U.S. of millions of dollars by filing more than 660,000 flawed background investigations. The Wall Street Journal reported that the Justice Department made the claims in a 25-page civil complaint that joined a whistleblowers' lawsuit against US Investigations Services, LLC in U.S. District Court in Alabama. USIS was the firm that conducted background checks on NSA leaker Edward Snowden, as well as Aaron Alexis, a defense contractor who fatally shot 12 people before killing himself at the Navy Yard in Washington, D.C. this past September. Federal officials...