Aafia Siddiqui, 36, is a Pakistani mother of three, an alumna of MIT, and a Ph.D. in neuroscience from Brandeis University. She is also accused of working for Al-Qaeda and was charged last week in New York City with attempting to kill American soldiers. Her arrest serves to remind how invisibly most Islamist infiltration proceeds. In particular, an estimated forty Al-Qaeda sympathizers or operatives have sought to penetrate U.S. intelligence agencies. Such a well-placed infiltrator can wreck great damage explains a former CIA chief of counterintelligence, Michael Sulick: "In the war on terrorism, intelligence has replaced the Cold War's tanks...