Federal investigators for the Office of Personnel Management alleged that USIS, the largest private provider of background checks for the government, repeatedly misled the government between 2008 and 2011 as to the thoroughness of the checks. The company vetted NSA leaker Edward Snowden in 2011. NSA chief Gen. Alexander said the surveillance program had disrupted 54 terrorist plots, of which 50 led to arrests or detentions, half of which occurred in Europe. Among the 54 foiled plots were 13 that developed inside the US. The Pentagon is updating rules of engagement for cyberwarfare and plans to add 4,000 people to US Cyber Command.