WASHINGTON (AP) - Defense Secretary Leon Panetta says the threat of computer attacks from Iran has grown and he says the Pentagon is prepared to take action.

A former U.S. official says authorities believe Iranian-based hackers are responsible for cyberattacks that devastated Persian Gulf oil and gas companies.

The former official is familiar with the investigation and says U.S. authorities believe the attacks were probably backed by Tehran and came in retaliation for the latest round of American sanctions.

Panetta, in a speech Thursday to business leaders in New York City, said they were probably the most destructive cyber assault the private sector has seen so far. He did not, however, directly link Iran to the Gulf attacks.