American commanders are fully aware that Iraqi (search) terrorists exploit their policy of employing locals on U.S. military bases but insist the practice will not stop, though some security measures may be tightened.

The vulnerability of the American stance was exposed on Dec. 21, when an Iraqi homicide bomber (search) dressed in a military uniform detonated his explosives at a mess hall at Forward Operating Base Marez in Mosul (search), killing 22 people including 14 U.S. servicemembers.

Since then, security has been tightened at chow halls in some camps, with military guards demanding proof of identification more often and not allowing backpacks. Officials say they are constantly reviewing procedures to make sure such an attack doesn't happen again, but insurgents infiltrating camps is unavoidable.

"They're trying to infiltrate the base as much as possible, taking pictures, videos drawing diagrams, grabbing people who are coming off base to intimidate them into giving them locations where different facilities are located on the base or torturing them until they do tell them," said Lt. Col. Dan Wilson, deputy for current operations for the 1st Marine Division. "We know it is active and ongoing."

Officials describe force protection as a game of cat-and-mouse, constantly refining tactics on base to counter changes by Iraq's insurgents.

One aspect the insurgents also appear to have exploited is the American desire to give Iraqi security forces a greater role, to treat them more as equals and to try to get them to do their jobs on their own, without U.S. supervision.

While Iraqis who work on bases are vetted, Americans acknowledge that they don't do security checks on Iraqi forces on base, instead leaving that task to their Iraqi counterparts.

"We don't do a systematic vetting process on Iraqi security forces, their government that does that," Wilson said. "There's a certain trust factor that goes along with the Marines working with them."

Wilson said top-level military staff had asked bases to re-evaluate how they go about force protection, but things like allowing Iraqis on base would not change. Wilson refused to say what sort of ideas were being discussed, only that the ideas were being passed around with the goal of enhancing security.

Some changes have been more visible. Guards at mess halls are stricter about enforcing a policy that badges be visibly displayed. At the gym at Camp Fallujah, only those with Department of Defense badges are now allowed.

Many U.S. bases employ dozens and dozens of Iraqi and other foreign contractors to drive trucks, do construction work and sweep trash. Iraqi work crews are usually accompanied by an escort. Some of the Iraqis live on base and don't tell their families or neighbors about the work they do, for fear of being attacked.

But with jobs so scarce in the country, they say there's little choice.

"Of course everybody is afraid, these people are criminals who will do anything to hurt people," said one Iraqi man working at Camp Fallujah, an electrician who identified himself as Mohammad. "But we can't find a good job except of these types of places."

Mohammad said he and his fellow workers live on the base and hail from Baghdad, far enough away that word hasn't spread about what they do. He said Iraqis are clamoring to get jobs on bases because there is no other option.

"In Iraq, our livelihood now depend on the Americans," he said. "This is what's best for us."

The workers he was with said they were generally pleased with the food, saying they liked the beef and chicken, as well as all the soda that is stacked in refrigerators at each end of Camp Fallujah's two mess halls.

American troops on the bases express widespread distrust about the Iraqis that work there, and have remarked that they all believe contractors are relaying intelligence back to insurgents on the outside.

But that won't lead to a change in policy, said Marine spokesman Lt. Lyle Gilbert.

"Contracting locals helps the economy. That's something we want to do," Gilbert said. "We want the Iraqi economy to flourish. We want them to have jobs, to have money, to get back on heir feet."

Gilbert said that closing off bases to Iraqis would be like "everybody in America closing their doors in fear and not going anywhere."

"We're here. They know we're here, and we know they're there. It's a fact of life," he said.