"I do think it's a genuine concern," says Stewart Baker, a lawyer and former senior official at the National Security Agency and the Department of Homeland Security. "I'd love to think it's overstated, but that view is supported more by wishful thinking than by analysis. If you judge adversaries by capabilities rather than intent, there's no doubt that anyone with a really strong cyberespionage capability can cause something that will feel like a cyber Pearl Harbor."
Some others aren't so sure that the world is full of big adversaries with substantial cyberespionage capabilities. In an article in Foreign Policy magazine headlined "Panetta's wrong about a cyber 'Pearl Harbor,' " John Arquilla says it's the "wrong metaphor."
"There is no "Battleship Row" in cyberspace," writes the professor of defense analysis at the Naval Postgraduate School in Monterey, Calif. "Pearl Harbor was a true ‘single point of failure.’ Nothing like this exists in cyberspace."
The logic behind creating the Internet, he says, was to ensure continued communications even after a nuclear war. Resilience is a key idea that shaped the structure of cyberspace, he says. Still, he's not entirely sanguine:
"Our armed services, increasingly dependent upon their connectivity, can be virtually crippled in the field by disruptive attacks on the infrastructure upon which they depend – but which are not even government-owned," he writes.
Still others say the whole concept is overblown.
"Digital Pearl Harbor is just a funding term, a way to get money for military and cybersecurity budgets," says John Robb, a former Air Force pilot who served in Special Operations Forces and is author of "Brave New War" about new modes of warfare. "It has no real relevance because we still live in a world dominated by nuclear weapons."