“If you’re in this program, it affects you from moving up,” said Bobby Devadoss, a Dallas lawyer who represents Mr. Abdel-Hafiz and some West Coast F.B.I. agents in the program. “You could be a superstar agent, but if you’re in this box, you’re in the box.”

Critics say inclusion in the program is not based on performance or behavior, but on shifting, ill-defined security risks. They say they have little legal recourse as the few challenges to the program brought in federal court have been denied on national security grounds.

“It would appear that agents have no idea what they do to get on the program, what they should do while on the program and what they should do to get off the program,” said Jonathan C. Moore, a New York lawyer who once represented an F.B.I. agent in the program. “Inclusion seems to be wholly discretionary, which means it could be caused by the whims of a supervisor who for whatever reason doesn’t think so highly of the agent.”

The F.B.I. began the program in 2002 to help screen scores of contract linguists for security clearances. The authorities feared that the new employees could be manipulated or coerced to help a foreign spy agency or a terrorist group. For example, a friend or relative overseas could be threatened with harm unless the F.B.I. employee provided secret information or otherwise cooperated with the spies or terrorists.

Image Gamal Abdel-Hafiz was hired in 1994 as an Arabic linguist.

As of April 2008, 314 contract linguists were in the program, according to a Justice Department inspector general’s office report in October 2009, the only publicly available figure. From fiscal years 2005 to 2008, the F.B.I. said, six contract linguists were either suspended or lost their top-secret clearance as a result of the program’s review, according to the report.

F.B.I. officials declined to say why those linguists had been suspended or to provide any updated statistics except to say that since the program was expanded in November 2005 to include all F.B.I. personnel, its ranks had grown to nearly 1,000 people. That is out of a total F.B.I. work force of 36,000 employees and thousands of contractors.