Brushing off threats of legal action and a broad effort to delete his presentation from conference materials, a security expert told Black Hat attendees on Wednesday that attackers can broadly compromise Cisco routers.

Mike has a number of good quotes in this story:

"I feel I had to do what's right for the country and the national infrastructure," he said. "It has been confirmed that bad people are working on this (compromising IOS). The right thing to do here is to make sure that everyone knows that it's vulnerable."

Lynn outlined a way to take control of an IOS-based router, using a buffer overflow or a heap overflow, two types of memory vulnerabilities. He demonstrated the attack using a vulnerability that Cisco fixed in April. While that flaw is patched, he stressed that the attack can be used with any new buffer overrun or heap overflow, adding that running code on a router is a serious threat.

"When you attack a host machine, you gain control of that machine--when you control a router, you gain control of the network," Lynn said.

During his presentation, Lynn outlined an eight step process using any known, but unpatched flaw, to compromise a Cisco IOS-based router. While he did not publish any vulnerabilities, Lynn said that finding new flaws would not be hard.

"People aren't looking at this because they don't think gaining control of a router is doable, but there are a lot of bugs to find," he said.

In a presentation that had all the hallmarks of good theater, Lynn stated several times that the information that he was presenting would likely result in legal action against him.

"What I just did means that I'm about to get sued by Cisco and ISS," Lynn said, joking later that he may be "in Guantanamo" by the end of the week.

However, Lynn argued that the seriousness of the attack left him no choice but to let people know the existence of the weakness in the software. Cisco plans in the future to abstract the architecture of the router operating system in the future, which could have a side effect of making a single attack work against all routers. Rather then knowing the various memory addresses, or offsets, needed to compromise systems, a single offset could work, Lynn said.

"What politicians are talking about when they talk about the Digital Pearl Harbor is a network worm," he said. "That's what we could see in the future, if this isn't fixed."