Lebanese fraudster became an agent for both the FBI and CIA

A Lebanese woman who managed to obtain sensitive jobs at both the FBI and CIA without proper background checks, then looked up her relatives on an FBI database, faces 16 years in jail.

As a tale of incompetence by the intelligence services, the tale of Nada Nadim Prouty is hard to beat. She arrived on a student visa in 1990 and, like tens of thousands of other foreign migrants, stayed on. Officials say her case is a cautionary tale of America's vulnerability to infiltration by foreign enemies.

Prouty, 37, pleaded guilty on Tuesday to using her security clearance to illegally access files on government computers about the Islamic terrorist group Hizbollah. She also confessed to fraudulently obtaining US citizenship through a sham marriage. After her wedding in 1990, Prouty worked as a waitress at Middle Eastern restaurants in Detroit, where she was recruited by the FBI in 1999. It is believed she was "talent spotted" to spy on the city's large Arab-American population. The FBI gave her full security clearance and then posted her to its Washington field office, which investigates crimes against US citizens overseas.

While there, she used her pass to gain access to restricted FBI computer files. According to court documents, she wanted to know if her sister and brother-in-law were being linked by the US to Hizbollah. In June 2003, she left the FBI to join the CIA as an undercover agent.

The FBI is wondering how Prouty was able to sail through its background checks, which included interviews with her current and former husband and with her relatives in Lebanon. She also passed a lie detector test with "no deception noted".

Stephen Kodak, a spokesman for the bureau, said it was trying to recruit so many agents, especially those with foreign-language backgrounds or from overseas, that it faced "special challenges" which it was now facing up to.

"Nada Prouty's guilty plea should serve as a solemn warning to those who pledged their allegiance to the US and then make the conscious decision to place America's interests at risk," added Brian Moskowitz, an FBI special agent in charge of the Immigration and Customs Enforcement (ICE) unit in Detroit.

"The ICE will do everything in its power to see that those who achieve this honour [of becoming a US citizen] by fraud and deception are brought to justice." Prouty's early years in the US were spent working at a chain of restaurants called La Shish, owned by her brother-in-law Talal Khalil Chahine. He is on the run and believed be in Lebanon with Prouty's sister, Elfat El Aouer. They were charged with tax evasion last year over a plot to conceal more than $20m in La Shish's profits which was funnelled back to Lebanon.

Adding to the CIA and FBI's paranoia, the court papers reveal that in 2002 El Aouer and Chahine attended a fundraiser in Lebanon where the speakers included Sheikh Muhammad Hussein Fadlallah, whom the US accuses of being a terrorist and Hizbollah's ideological leader.

There is no evidence that Prouty passed US secrets to Hizbollah. One US official, who spoke anonymously to the Washington Post yesterday, said: "At this point, there is no reason to treat this as a counter-terrorism case involving a hostile group."