The Cisco hacking scene has been pretty quiet for the past three years, but at this week's Black Hat hacker conference in Las Vegas, there's going to be a little noise.

Security researchers will give talks on rootkits and new hacking and intrusion-detection software for the routers that carry most of the Internet's traffic.

Three years ago, security researcher Michael Lynn shined a spotlight on Cisco's products when he talked about how he ran a simple "shellcode" program on a router without authorization. Lynn's controversial talk was the biggest story at Black Hat 2005. He had to quit his day job to get around a company prohibition on discussing Cisco, and both he and the conference organizers were quickly sued by Cisco. The networking company argued that Lynn's presentation slides contained information that violated the company's intellectual property rights, and Lynn's talk was literally ripped out of the conference materials package. In a settlement agreement, the researcher was barred from further discussing his work, but copies of his presentation (pdf) were posted online.

Today, Cisco Chief Security Officer John Stewart is remarkably candid about the experience, saying that his company acted for the right reasons -- protecting its customers and intellectual property -- but went too far. "We did some sort of silly things," he said. "Which is why I personally sponsored Black Hat at the platinum level ever since. Because I think we had some atonement to do."

Lynn wasn't without a job for long. He was quickly snatched up by Cisco competitor Juniper Networks, but for a few years after his talk, there wasn't much public discussion of Cisco hacking, according to Jeff Moss, Black Hat's director.

Moss believes that economics may have driven some Cisco researchers underground. Any code that exploits Cisco vulnerabilities is so prized that any hacker who chooses to disclose his findings, rather than sell them to a security company or government agency, is often giving up a lot of money, Moss said. Mike Lynn's vulnerability was worth about US$250,000, he reckons.

But this year things have opened up. Black Hat organizers plan three talks on Cisco routers and the Internetwork Operating System that they run. "All of a sudden this year a lot of stuff has been breaking loose," Moss said.

Lately, with Microsoft Windows no longer the fertile ground for bug hunting that it once was, researchers are looking at other products to hack. And Cisco's routers are an interesting target. They command more than 60 percent of the router market, according to research firm IDC.