U.S. military networks are seeing "hundreds of thousands of probes a day," according to alarming new statistics revealed this morning by the Army general nominated to head the U.S. military's new Cyber Command. But beyond that scary headline, it's not clear if the threat is what it's cracked up to be.

In a Senate Armed Services Committee confirmation hearing today, Lt. Gen. Keith Alexander said the Pentagon was "alarmed by the increase, especially this year," in the number of attempts by outsiders to scan military networks for potential weaknesses and vulnerabilities.

As Wired.com's Threat Level has noted, that kind of language is certain to grab the attention of senators, and top policymakers. But the reality is a bit more prosaic. Those probes don't necessarily translate into hostile action, Alexander added: "They may scan the network to see what kind of operating system you have to facilitate ... an attack."

Still, the confirmation hearing for Alexander, who has been tapped to lead the Pentagon's new Cyber Command is also shaping up as a fascinating discussion of the potential rules of engagement in cyberwarfare. But it's also likely to help drum up business for more scare-mongering government IT consultants.

Among other things, senators are discussing some of the hypothetical scenarios for how the U.S. military might respond if its networks – or civilian networks – came under online assault. Sen. Carl Levin (D-Michigan), the chairman of the committee, quizzed Alexander on how the military might respond if an adversary launched an attack through a neutral country – or through computers owned by U.S. entities. Would the U.S. military have the authority to mount a defense, or stage a possible counterattack?

Alexander said the command has established rules of engagement that spell out what it can do to defend its networks, where it can go and how it can block attacks. It would rely on an "execute order" from the combatant commander (i.e., the four-star geographic commander) to block an attack in an overseas theater.

A domestic attack, however, might complicate matters. The hearing is also raising some important (and very sticky) legal issues, such as the extent to which the Department of Defense would have to step in to defend government civilian networks or private U.S. networks.

The general said the Department of Homeland Security would have the lead, but the military's Cyber Command would have a supporting role. However, the legal issues surrounding an attack that was routed through U.S. domestic entities, he conceded, would be "more complex" because of civil liberties and privacy issues.

[Image: Senate Armed Services Committee]