Experts said the flaw, disclosed Tuesday by the British government, affects the underlying technology for nearly all Internet traffic. Left unaddressed, they said, it could allow hackers to knock computers offline and broadly disrupt vital traffic-directing devices, called routers, that coordinate the flow of data among distant groups of computers.
"Exploitation of this vulnerability could have affected the glue that holds the Internet together," said Roger Cumming, director for England's National Infrastructure Security Coordination Centre.
The flaw affecting the Internet's "transmission control protocol," or TCP, was discovered late last year by a computer researcher in Milwaukee, Paul "Tony" Watson, 36, who said he identified a method to reliably trick personal computers and routers into shutting down electronic conversations by resetting the machines remotely.
Routers continually exchange important updates about the most efficient traffic routes between large networks. Continued successful attacks against routers can cause them to go into a stand-by mode, known as "dampening," that can persist for hours.
Experts previously maintained such attacks could take between four years and 142 years to succeed because they require guessing a rotating number from roughly 4 billion possible combinations. Watson said he can guess the proper number with as few as four attempts, which can be accomplished within seconds.
"The biggest concern is (the effect on routers) because of the risk of bringing down the Internet or severely disrupting traffic on the Internet," Watson said.
Already in recent weeks, some U.S. government agencies and companies operating the most important digital pipelines have quietly fortified their own vulnerable systems because of early warnings communicated by some security organizations. The White House has expressed concerns especially about risks to crucial Internet routers, since attacks against them could profoundly disrupt online traffic.
"Any flaw to a fundamental protocol would raise significant concern and require significant attention by the folks who run the major infrastructures of the Internet," said Amit Yoran, the U.S. government's cybersecurity chief. The new flaw has dominated discussions since last week among experts in close-knit security circles.
The public announcement coincides with a presentation Watson expects to make Thursday at a popular Internet security conference in Vancouver, where Watson said he will reveal full details of his research.
Watson, who runs the www.terrorist.net Web site, predicted that hackers will understand how to begin launching attacks "within five minutes of walking out of that meeting."
"It's fairly easy to implement," Watson said. "Someone walking out of the conference would immediately understand. No matter how vague I am, people will figure it out."
By Ted Bridis