Did a Congressman just acknowledge the US took down North Korea's internet in December?

Rep. Michael McCaul hinted at a think tank event on Tuesday that the US may have been responsible for North Korea's massive internet outage in late December.

He made the comment in passing when an attendee at the event asked him about how the US could proportionally respond to cyber threats from other countries. McCaul, who as the chairman of the House Homeland Security Committee is in a good position to know, mentioned Stuxnet as one example of a US cyber response. The destructive virus, which was discovered in 2010 after reportedly being developed by Israel and the US, caused huge damage to Iran's nuclear program.

McCaul, in the course of his answer on how the US responds to cyber threats, then mentioned North Korea: "There were some cyber responses to North Korea," he said, referring to the country's alleged role in the November hacks against Sony Pictures.

Though he did not explicitly confirm long-held suspicions that US cyberattacks were responsible for North Korea's mass internet outage, McCaul's comments have come as close as any official US statement ever has to acknowledging a role.

The comments, made at a cybersecurity policy event hosted by the Center for Strategic and International Studies, were first reported by Bloomberg reporter Chris Strohm and confirmed by a source with knowledge of the event.

Here's the backstory: Hackers attacked Sony Pictures in November, releasing private emails and other embarrassing details to the world. They claimed this was in retaliation for the film The Interview, a comedy that portrayed the assassination of North Korean leader Kim Jong Un. The US later accused North Korean government hackers of responsibility in December and President Obama warned of a "proportional response."

A few days later, on December 21 and 22, internet connectivity between North Korea and the outside world was severed completely. Suspicion immediately fell on the US, which the Obama administration would neither confirm nor deny.

Another common theory has been that the Chinese government cut North Korea's internet; most North Korean connections are routed through China, and Beijing has at times punished North Korea for its aggressive behavior.

Yet another hypothesis is that non-government hackers, working on their own, took it upon themselves to shut down North Korea's internet as punishment for the Sony hack. (I have been skeptical of this theory, as hacker communities can be heavy on bragging and lighter on demonstrated action, and some have made implausible claims about hacking North Korea before.)

McCaul's comments were vague enough to leave open the possibility that it was not the US government that attacked and shut down North Korea's internet, although that was certainly an implication of mentioning the cyberattack in the course of discussing specific US cyber actions. He was also vague on what he meant by "responses"; it is possible, then, that shutting down North Korea's internet may not have been the only measure taken.