It would have been the most far-reaching case of computer sabotage in history. In 2003, the Pentagon and American intelligence agencies made plans for a cyberattack to freeze billions of dollars in the bank accounts of Saddam Hussein and cripple his government’s financial system before the United States invaded Iraq. He would have no money for war supplies. No money to pay troops.

“We knew we could pull it off  we had the tools,” said one senior official who worked at the Pentagon when the highly classified plan was developed.

But the attack never got the green light. Bush administration officials worried that the effects would not be limited to Iraq but would instead create worldwide financial havoc, spreading across the Middle East to Europe and perhaps to the United States.

Fears of such collateral damage are at the heart of the debate as the Obama administration and its Pentagon leadership struggle to develop rules and tactics for carrying out attacks in cyberspace.