Israeli officials say Iran, which has been hit several times by mysterious computer viruses, has launched an "ambitious plan" to boost its cyberwar capabilities and is investing $1 billion in cutting-edge technology.

If the claim is correct, the Iranian effort underlines what veteran analyst Mahan Abedin calls the "stunning achievements in the intelligence, electronic and cyberwarfare fields" against the West by Tehran's security services in recent months.

The Iranian move is in apparent response to a significant increase in intelligence operations against the Islamic Republic by the United States, Britain and Israel as tensions over Tehran's contentious nuclear program escalate in a region already gripped by uncertainty and regime change.

"The dramatic spike in CIA activity inside Iran in 2011 has reinforced the Iranian leadership's conviction that the Western powers are set on a confrontation and a possible military showdown with the Islamic Republic," Abedin observed in an Asian Times Online analysis Thursday.

"There is a fear in Tehran that Western agencies -- working directly and indirectly with radical opposition elements -- will try to incite riots and disorder, similar in style if not scope to the ones that rocked the Iranian capital in June 2009 following the disputed presidential elections."

Iran's Ministry of Intelligence and Security, which has been tightening its operations for some time, claims it arrested a CIA spy, a former U.S. Marine of Iranian origin named Amir Mirza Hekmati.

It said his mission was to infiltrate the MOIS and feed it disinformation. Hekmati, 28, was reportedly arrested in September but it was only announced Dec. 17. The following day, state television broadcast what it said was a taped confession by Hekmati.

Earlier, Iran said it downed an ultra-secret U.S. RQ-170 Sentinel surveillance drone operating out of Afghanistan, allegedly by electronically hijacking its controls.

Washington admitted to the loss of the CIA-owned Sentinel, which Iran said was recovered intact. Its highly classified electronic systems were a major prize for Iranian intelligence and a serious blow to the Americans.

In November, Iran said it had arrested 12 members of a CIA spy ring. That came hard on the heels of the reported capture of 30 alleged CIA agents in late May.

At the same time, Hezbollah in Lebanon, Iran's most important Arab proxy, claimed it seized several people it said had been recruited by CIA officers working out of the U.S. Embassy in Beirut.

Arab intelligence sources said the counterintelligence sweeps in Tehran and Beirut were connected.

Iranian intelligence, particularly the intelligence arm of the elite Islamic Revolutionary Guards Corps, has long worked hand-in-hand with Hezbollah's security wing, widely considered to be one of the most effective counterintelligence outfits in the Middle East.

Hezbollah, with Iranian technical help, has been able to electronically penetrate the surveillance systems of the spy drones Israel has been deploying over Lebanon for the last decade or so -- a possible link to the RQ-170 debacle.

These setbacks have been grudgingly confirmed by U.S. officials, which Abedin notes, "is suggestive of a major American intelligence defeat, if not a full-blown disaster."

"The exposure of the agents in Lebanon was apparently due to extremely poor tradecraft on the part of the CIA officers running the operations," said former CIA official Philip Giraldi, "while the Iranian roll-up was due to badly conceived and insecure Internet communications that were identified by the Iranian security services."

Last January, Tehran said it had broken a spy ring run by Israel's Mossad intelligence service.

It has been widely blamed for the assassination of several Iranian nuclear scientists and several bombings, including a military base in November in which dozens of Iranian Shehab ballistic missiles were supposedly blown up.

Abedin says the Iran November roundup of alleged CIA spies indicates that "the CIA is operating a lower threshold of quality control in terms of agent recruitment and managed.

"Second, there are signs that MOIS is moving steadily in the direction of making Iran a forbidding space for hostile foreign intelligence services."

There have been suggestions that the 30-strong CIA ring was betrayed by an Iranian student who'd been approached by a quasi-academic institution in Malaysia offering grants and scholarships.

Iranian Intelligence Minister Heydar Moslehi indicated most of the suspects were junior scientists or students who traveled abroad frequently.