The effort, involving the National Security Agency, the CIA and Israel’s military, has included the use of destructive software such as the Stuxnet virus to cause malfunctions in Iran’s nuclear-enrichment equipment.

The emerging details about Flame provide new clues to what is thought to be the first sustained campaign of cyber-sabotage against an adversary of the United States.

“This is about preparing the battlefield for another type of covert action,” said one former high-ranking U.S. intelligence official, who added that Flame and Stuxnet were elements of a broader assault that continues today. “Cyber-collection against the Iranian program is way further down the road than this.”

Flame came to light last month after Iran detected a series of cyberattacks on its oil industry. The disruption was directed by Israel in a unilateral operation that apparently caught its American partners off guard, according to several U.S. and Western officials who spoke on the condition of anonymity.

There has been speculation that Washington had a role in developing Flame, but the collaboration on the virus between the United States and Israel has not been previously confirmed. Commercial security researchers reported last week that Flame contained some of the same code as Stuxnet. Experts described the overlap as DNA-like evidence that the two sets of malware were parallel projects run by the same entity.

Spokesmen for the CIA, the NSA and the Office of the Director of National Intelligence, as well as the Israeli Embassy in Washington, declined to comment.

The virus is among the most sophisticated and subversive pieces of malware to be exposed to date. Experts said the program was designed to replicate across even highly secure networks, then control everyday computer functions to send secrets back to its creators. The code could activate computer microphones and cameras, log keyboard strokes, take screen shots, extract geo­location data from images, and send and receive commands and data through Bluetooth wireless technology.

Flame was designed to do all this while masquerading as a routine Microsoft software update; it evaded detection for several years by using a sophisticated program to crack an encryption algorithm.

“This is not something that most security researchers have the skills or resources to do,” said Tom Parker, chief technology officer for FusionX, a security firm that specializes in simulating state-sponsored cyberattacks. He said he does not know who was behind the virus. “You’d expect that of only the most advanced cryptomathematicians, such as those working at NSA.”