Sandy Berger, the former national security adviser to President Bill Clinton who was convicted for stealing and destroying top secret documents, is now advising Sen. Hillary Clinton's presidential campaign, FOX News confirms.

The New York Democrat's campaign said Monday that Berger is an informal, unpaid adviser to the campaign. He has been a longtime friend of both Clintons.

Aides to the campaign were unapologetic about Berger's advisory role, noting he is not a central figure but has valuable and welcome input that he is providing voluntarily.

The (Washington, D.C.) Examiner reported the connection Monday.

The Examiner reports the arrangement with Berger is similar to one with Sen. John Kerry's 2004 presidential campaign, for which Berger provided foreign policy advice. Kerry, however, severed the relationship with Berger once charges that he stole the classified material became public.

In 2003, Berger took sensitive national security documents from the National Archives in the lead-up to the 9/11 commission hearings, at times stuffing them into his socks, and one time hiding papers under a construction trailer near the archives building in downtown Washington.

Berger, who at first denied any wrong-doing, later pleaded guilty and was fined $50,000 and sentenced to two years probation. He also lost his security clearance for three years.