While most Americans are familiar with al-Qaida, they’re less knowledgeable about a group spreading terror within U.S. inner cities: Mara Salvatrucha. Also known as MS-13, the Maras have 20,000 North American members. Mara cadres have set up in many American cities, creating the beginnings of a national command hierarchy, with some Maras on the East and West coast reporting directly to and paying gang dues to leaders in Central America. As these cadres grow and learn, they become more dangerous, and already they have begun to actively target law enforcement officers. Although the FBI and law enforcement agencies have tried to contain them using anti-racketeering statutes, which allow prosecutors to attack the structures of organized crime, the real problem lies beyond the border.