Washington (CNN) -- The United States believes Iran is behind cyber attacks on American banks and the oil industry in the Middle East, officials said.
Although they have not made such an assertion publicly, officials have characterized the attacks that occurred in recent months as initiated by a "state actor."
And one official said that U.S. intelligence has observed and tracked the attacks coming from Iran. The official would not offer details, but said there is a belief that those involved were surrogates working with the Iranian government.
"We strongly believe there is a relationship between the people typing the code and people running the government," the official said.
The development comes as the United States has become more concerned about Iran and cyber security.
"It certainly is the case that Iran is improving its capabilities in the cyber field. We're paying attention. We are concerned about their increasing ability to operate in this realm," an intelligence official said.
Defense Secretary Leon Panetta noted the energy and banking attacks in a speech last week, and warned that United States must beef up its cyber defenses or risk a potentially devastating strike.
Panetta did not publicly say that Iran was behind the attacks.
Calling it a "pre-9/11 moment," Panetta said he was worried about a significant escalation of attacks and highlighted a cyber virus known as "Shamoon." The virus infected the computers of major energy firms in Saudi Arabia and Qatar this past summer.
In Saudi Arabia, more than 30,000 computers were rendered useless by the attack on the state oil company ARAMCO. Ras Gas was affected in Qatar.
Panetta said the attacks were probably the most devastating to ever hit the private sector.
Iran denied any involvement in the attack on the oil industry, according to a report broadcast Monday on PRESS TV, a government-run news agency.
"One of the main aims of the United States is to make itself look like the victim," said Mehdi Ahkavan Bahabadi, the director of the Iran Cyberspace Center.
The report noted Iran itself has been the victim of numerous online assaults, including Stuxnet, a complex cyberattack against its nuclear program believed to have been created by American and Israeli programmers.
Panetta's speech also covered recent attacks against large U.S. banks, which hit with unprecedented speed and disrupting services to customers.
While the attacks did not do any significant damage or result in any financial losses, it caught the attention of U.S. intelligence, according to officials.
Officials said they have not heard any talk with in the government regarding a possible retaliatory strike for the attack on the banking system.
The New York Times reported there seems to be no conclusive evidence that the cyber attacks were sanctioned by the Iranian government. But U.S. officials have begun to focus suspicion on a recently created Iranian military unit called "cybercorps."
The unit was developed in response to American and Israeli cyber attacks on the Iranian nuclear enrichment plant at Natanz.
Suzanne Kelly and Pam Benson contributed to this report.