Western countries are very concerned about some of their own Moslem citizens quietly joining ISIL (Islamic State in Iraq and the Levant) and either going to Iraq or Syria to actually fight for this very radical Islamic group (even al Qaeda condemns it) or staying in their home country and trying to organize terror attacks there. On the plus side, ISIL prospects are easier to find because they are basically recruited from all those people who had, at one time or another, professed allegiance to (or interest in) al Qaeda. This poaching is (one of many reason al Qaeda hates ISIL. Those in the West who have shown interest in al Qaeda are often eventually detected and in most cases monitored until and if they break a law. So far that approach has worked pretty well, especially after a some of these people actually carried out attacks in Britain and Spain and made the monitoring more popular. The monitoring tightened up, there were more arrests and prosecutions and now people on these watch lists are being used to indicate who is seeking to upgrade from naughty (al Qaeda) to nasty (ISIL). There are no press releases about how this works, because many of those being monitored do not know they are being watched.
There have been several attempts to count the number of Western Moslems who have gone to Syria or Iraq, joined ISIL and fought for that group. The best unclassified numbers indicate that up to 3,000 Western Moslems have gone off to fight for ISIL and at least a thousand of them are there right now. It appears that about 30 percent are from France, 18 percent from Britain, 14 percent from Germany, 11 percent from Belgium, nine percent from Australia and smaller percentages from the Netherlands, Canada, the United States and Spain (in that order, with Spain accounting or about two percent). Most of these Moslems were born in Moslem countries or have parents or grandparents who were. Less than ten percent are locals who converted to Islam. These are considered the most dangerous because they don’t look like most Moslems (who tend to be from the Middle East, Africa or Asia). But the converts are also more prone to later have doubts and backslide. Some have been turned into double agents, spying on terror groups for their homeland and other Western intelligence agencies.