Leandro Aragoncillo, the former vice-presidential aide accused of passing U.S. intelligence to opposition Philippine politicians, may be the most recent case of an alleged spy in the White House, but he's not the first.
"You've had other instances where other individuals have leaked … from the White House, as well as other agencies," said Peter Earnest, a 36-year veteran of the CIA and the founding executive director of the International Spy Museum in Washington.
The history of spying for and against the United States dates back to before the nation's founding. And that history can be murky: To this day, all that's known of some spies are their code names. Some doubt the guilt of convicted spies. And some historical figures who never faced espionage charges now are widely thought to have been moles.
Some of those supposed spies include former officials with White House access.
For example, Earnest said, newly-declassified U.S. and Soviet intelligence backs longtime allegations that Alger Hiss, part of the presidential delegation to the Yalta conference that divided Europe after World War II, and Lauchlin Currie, a longtime U.S. government official and aide to President Franklin D. Roosevelt, were Soviet spies in the 1930s and 1940s.
More recently, in 1997, the FBI was said to be looking for an Israeli agent identified only by the code name "Mega" in decrypted communications that suggested he had penetrated the Clinton White House.
Neither Hiss nor Currie was convicted of espionage. Both maintained their innocence, and continue to have defenders even after their deaths in the 1990s.
Hiss, though accused of spying during highly-publicized trials in the late 1940s, ultimately was convicted of perjury. Much of the evidence against Currie remained classified during his lifetime, perhaps the reason he never was tried. But the native Canadian, a naturalized U.S. citizen, was blocked from re-entering the United States in the 1950s. He moved to Colombia, ultimately gaining citizenship there and becoming a celebrated government economic advisor.
Frederick Wettering, a 35-year CIA veteran, now retired and teaching a course on the history of espionage at Lake-Sumter Community College in Florida, said turncoats historically tend to volunteer as spies, rather than get recruited -- and they have displayed a variety of motives.
"The acronym I use is MIRE," Wettering said. "Money, ideology, revenge and ego are the main reasons they do that."
The Revolutionary War turncoat Benedict Arnold -- a recruit of the British, not a volunteer -- may have changed sides as revenge for professional slights or for relief from financial problems. Several spies in the 1930s and 1940s volunteered to spy for the Soviet Union because of ideology.
More-recent spies seem to have been in it for the money: John A. Walker and Aldrich Ames, spies for the Soviets who pleaded guilty in 1985 and 1994, respectively, "did it strictly for the money," Wettering said. Robert Hanssen, an FBI agent sentenced in 2002, was for decades a highly-paid spy for the Soviets and then the Russians.
Officials told ABC News that former Philippine President Joseph Estrada and his aides used small amounts of money and appeals to ethnic loyalties to recruit Aragoncillo, 46, a naturalized Filipino-American FBI analyst and former White House aide to vice presidents Al Gore and Dick Cheney. Aragoncillo is said to have been a half-million dollars in debt.