Obama raised concerns that the Stuxnet program, code-named Olympic Games, would embolden other countries, terrorists and hackers to use similar attacks, but concluded that the U.S. had no other options available against Iran, the Times story said.

The goal of the attacks was to gain access to the industrial computer controls in Iran's Natanz nuclear plant, the story said. The U.S. National Security Agency and a secret Israeli cyberunit developed the Stuxnet worm, the story said.

The report that the U.S. and Israel were behind the Stuxnet attack didn't surprise Snorre Fagerland, senior virus analyst with Norman, an IT security vendor in Lysaker, Norway. The Stuxnet worm was "orders of magnitude" more complex and sophisticated than previous cyberattacks, he said, and the creation of the malware would have needed significant resources.

It would have taken a team of 10 to 20 people to write Stuxnet, Fagerland said.