The CIA isn't allowed to spy on U.S. citizens, but that doesn't mean it can't help the New York Police Department do it. According to an AP investigation, after the Sept. 11 attacks the CIA helped the NYPD set up an intelligence unit that often took aggressive measures in an attempt to detect terrorist plots. The department sent undercover officers known as “rakers” into Muslim neighborhoods and sent informants known as “mosque crawlers” to monitor sermons, even when there was no evidence of wrongdoing. It created a “Demographics Unit” to match undercover officers with particular communities of the same ethnicity and sent those officers to look for suspicious behavior. If the FBI were to adopt these tactics, it would violate the Privacy Act. The NYPD denies that the Demographics Unit exists and says it only follows leads.