Espionage Case Breaches the White House

Aragoncillo began working at the White House in 1999. Officials are now trying to learn how he landed the job, when he started spying, and how he escaped detection for so long.

"Of course, it is a source of embarrassment when you find out that this kind of activity has been carried out literally right under your nose," said Martin, the former espionage prosecutor.

According to friends, in addition to his work for Cheney and Gore, Aragoncillo claimed he also worked with President Clinton and Condoleezza Rice when she was the national security advisor.

ABC News' Vic Walter, Avni Patel and Rhonda Schwartz contributed to this report.