The Muslims of America organization recruits in prisons, and has already produced a number of Islamic terrorists. What worries the FBI is the many more members who talk-the-talk, but have not yet moved to the walk-the-walk phase yet. Even if these groups are not actively carrying out terrorist acts, their preaching and everyday conversations indicate they would provide support services for any "holy warriors" that came knocking.
These groups have survived because they have learned how to work the system, including the FBI, and whatever counter-terrorism mojo that gets thrown at them. A major part of their defenses is their insularity, even from other Moslems. In fact, Jamaat ul Fuqra considers less conservative Moslems as heretics. Many of the Fuqra folks prefer to live out in the country, and create as much isolation for themselves as possible. Finding out what's going on in these groups is much more difficult than with people in the general Moslem population. While most Moslem-Americans are loyal citizens, and willing to send in tips about possible terrorist groups, outfits like Jamaat ul Fuqra just don't do that sort of thing, and react violently if they find any of their members doing so.
On the plus side, many of these extremist or conservative Moslem groups know, or suspect, that they are being watched. Any move to carry out a terrorist attack would bring the law down on them and, their families. So far, the only terrorist action out of these groups have been false starts or suspicious, not indictable, activity. But the potential is there, and it's scary.
As the FBI digs deeper into the world of Islamic extremist groups in the United States, it has encountered a growing number of them operating in rural areas. Jamaat ul Fuqra is a group that began in Pakistan, where most members still reside, but has spread to North America over the last two decades. Many members have been busted for various crimes, usually ones related to fraud and abuse of social welfare programs.