No mean feat
However, any attacker looking to exploit this vulnerability would likely have a hard time, security experts say. Not only is it inordinately difficult to identify machines that are vulnerable, but the attacks themselves are quite hard to execute.
And because the flaw has been known for so long, it's unlikely that there are many TCP implementations that are still vulnerable to such attacks.
"This is extremely difficult to do. It's a theoretical attack," said security expert Steve Gibson, of Gibson Research. "It's weird that they're talking about something like this. It's as old as the hills."
While they acknowledge that it takes a very knowledgeable cracker to exploit the TCP flaw, Guardent officials defended the timing of their advisory and said it's only a matter of time before someone develops a set of tools to do the job and posts them on the Internet.
"The hard part was the reduction of this from theory to practice," said Jerry Brady, vice president of research and development at Guardent. "But if someone makes a tool for this available, it wouldn't take a very experienced person to [launch an attack]."
Guardent officials alerted CERT and the affected vendors to the problem before making it public.
"We're trying to break new ground here," Brady said. "We were intentionally vague about the details of the problem. We want to work with the vendors to fix this."
