Iraq. Iraqi and Coalition intelligence estimates that infiltration of foreign fighters into Iraq is averaging about 75 a month (with a range from two dozen or so up to 100), which is down significantly from 2005, when the average was about 125 a month. Reportedly, about 40 percent of the fighters are Jordanians or Saudis, another 20 percent are Syrian, another 30 percent seem to have African origins, and the balance come from Moslem communities all across the world, including Europe.
The 258 new border forts, and thousands of newly trained border police have seriously cut into illegal border crossings. While the border police caught about 1,500 people trying to cross illegally last year, they have caught 1,940 in the first four months of this year alone. Examination of captured documents, and interrogation of those border crossers arrested provides pretty accurate information on how many are making it across. Another factor in halting the illegal crossings is enlisting the Sunni Arab tribes along the border. By offering rewards for catching illegal crossers, the tribesmen have been out there looking as well (although the tribesmen are subject to accepting a large bribe to let the illegal crossers go.)
Surprisingly, very few infiltrators have been from Iran. The favored route into Iraq still seems to be through Syria, which seems to be taken by 70-75 percent of the infiltrators.