Denial-of-service attacks that target and use misconfigured network routing equipment pose an "imminent and real threat" to Internet security, says a report from the CERT Co-ordination Centre at Carnegie Mellon University. Unlike denial-of-service attacks that involve individual servers, a router-based attack is harder to stop and could result in service disruptions across large swathes of the Internet.
"Routers form the backbone of the Internet," said Kevin Houle, a member of CERT's team. "So attacks that involve routing equipment raise the potential of entire sections of the infrastructure being [disrupted]."
According to Houle, CERT has received an increasing number of reports of intruders taking unauthorised control of routers by using vendor-supplied default passwords. Once inside, the router's configuration and protocol information can be easily modified to misdirect Internet traffic. By targeting critical routers, such as those belonging to a major service provider, large sections of the Internet could be shut down, Houle said.
"Once people start attacking routers in this manner, all hell will break loose," said K. Narayanaswamy, chief technical officer at Cs3, a Los Angeles-based security firm. "It's like taking the signs on a highway and pointing them in all the wrong directions."
The industry has long been aware of router vulnerability, but it assumed critical importance following the September 11 attacks on the US and the heightened threat of cyber terrorism, Narayanaswamy added.
Intruders can also use routers to scan networks for vulnerable systems and as launch points for the more traditional denial-of-service attacks, which involve flooding a network with useless data, CERT warned. While misconfigured routers are the most vulnerable, intruders are also developing other ways of breaking into secure routers, according to analysts.
Generally, critical routers are much harder than Web servers to find, and therefore to attack, on a network, said Ted Julian, chief executive of the US vendor Arbor Networks.
Unlike vulnerable servers, which are often found by automated scanning tools, breaking into routers requires more work to identify the crucial routers to attack, Julian said. But if they are found and compromised, the resulting attacks could be devastating, he said.
Although Arbor sells tools to mitigate the effect of a denial-of-service attack targeting servers, there is little available to deal with router-based threats.
"This is a real threat that is going to be even harder for the authorities to stop," said Ralph Kuntz, chief technology officer at Hamilton Scientific, an application service provider for health care providers. One of Hamilton's routers was broken into earlier this year and was used to scan networks for vulnerable servers. The company learned of the compromised router only after receiving threatening letters from companies that had been scanned.