Amid a series a recent cyberattacks on Iranian industrial sites, Tehran is reported to be strengthening its cyberwarfare capabilities in a widening covert war with the United States and Israel.

The Islamic republic, one of the world's top oil exporters, has been steadily building its cyberdefenses since its nuclear program was sabotaged in 2010 by the Stuxnet computer worm, which reportedly was planted by the United States or Israel.

Last week, U.S. Air Force Gen. William Shelton warned that the Tehran regime has significantly boosted its cyberwarfare program since the Stuxnet attack on the uranium enrichment center at Natanz in central Iran.

Iran's official media claims that other nuclear facilities have been hit by Stuxnet since then as part of the U.S.-Israeli effort to wreck Tehran's suspected plans to develop nuclear weapons.

Over the last three years, Iranian industrial facilities, including the major Kharg Island oil export terminal in the northern Persian Gulf, as well as communications networks and banking systems have come under cyberattack.

So the Iranians clearly need to acquire more advanced cyberdefenses while they seek to develop offensive systems.

Shelton, who's head of the U.S. Air Force Space Command and oversees its cyberoperations, cautioned that Iran was a serious threat in cyberwarfare.

"They're going to be a force to be reckoned with, with the potential capabilities that they'll develop over the years and the potential threat that they'll represent to the United States," he said.

Washington has blamed Tehran for recent attacks on the United States, including a wave of hits on the banking system in late 2012.

Israel, too, has reported a marked upsurge in cyberattacks in recent months.

Iran's media reported in December the republic's Joint Chiefs of Staff had established a "soft war" headquarters to oversee defenses against cyberthreats from the United States and Israel.

On Jan, 15, Iran's Fars News agency quoted Brig. Gen. Ahmed Reza Pourdastan, commander of Iranian ground forces, as saying, "We've been equipped with electronic warfare systems so as not to remain just a defending force and rather to become able to jam the enemy's communications systems."

There's been a lot of speculation about what Iran's offensive cybercapabilities amount to.

But it's clear that the Tehran has been investing heavily in offensive cybercapabilities, and has reportedly undertaken several cyberoperations against U.S. and Israeli military and civilian infrastructure in recent months.

In mid-2012, Western intelligence sources estimated Iran had spent $1 billion in recent years to upgrade its cybercapabilities, often using advanced hardware and software smuggled from the West.

In July 2012, two leading cybersecurity companies, Seculert of Israel and Kaspersky Lab of Russia, reported uncovering a cyberespionage campaign, which reportedly targeted five Middle Eastern states using communications tools written in Farsi, the Iranian language.

They named the malware Mahdi, after the Shiite Muslim messiah. The experts said they'd identified 800 targets, including critical infrastructure companies, financial service firms and government embassies in the United States, Israel, Saudi Arabia and the United Arab Emirates.

Saudi Arabia's state oil giant, Aramco, and the state-owned RasGas company that exports the emirates' natural gas, were hit by Mahdi in August.

The damage was reported to be minimal, with oil and gas production unharmed. But it was a sharp wake-up call that Tehran was on the ball.

On Dec. 31, Iran's media reported Iranian forces had carried out what they termed cyberwarfare operations during major naval exercises in the strategic Strait of Hormuz, the only way in and out of the Persian Gulf and a vital oil supply route.

Iran's operations against U.S. drones on surveillance missions as part of the armed confrontation between U.S. and Iranian forces in the Persian Gulf indicate a growing sophistication.

On Dec. 4, 2011, Iran claimed it brought down a CIA RQ-170 Sentinel drone flying from Kandahar in neighboring Afghanistan by hacking into its control system when it was 140 miles inside Iranian airspace.

U.S. officials insisted the bat-winged Sentinel, built by Lockheed Martin, had malfunctioned and crashed in Iranian territory.