Hackers armed with a Web browser and a rigged SWF (Shockwave) file can fire code execution exploits at most modern Wi-Fi routers, according to a warning from researchers at the GNUCITIZEN think-tank.
The researchers, Adrian Pastor and Petko D. Petkov (pictured left), have found an easy way to use Shockwave files embedded on Web pages to silently launch a four-step attack to take control of any router that use the UPnP (Universal Plug and Play) protocol.
In an interview over IM, Petkov said the attack would work against "99 percent of all routers" running around the world.
"Using what we know, it is trivial to construct a massive router botnet," Petkov declared.
The attack scenario, he explained, depends on the fact that most modern routers run with UPnP enabled by default. Because the UPnP SOAP (Simple Object Access Protocol) service can be accessed without authorization over the default Web Admin interface, a rigged Flash file can send arbitrary SOAP messages to the router's UPnP control point-- effectively allowing the attacker to reconfigure the device to enable further attacks.
Petkov outlined a scenario where an attacker can change the primary DNS server on the router to turn the network it controls into a zombie for malicious use.
"It is also possible to reset the admin credentials and create the sort of onion routing network all bad guys want. Many routers come with Layer3 portforwarding UPnP service. This is also a potential vector that attackers can use. In cases like this, they will simply expose ports behind the router on the Internet-facing side," he explained. [ ALSO SEE: Month of Kernel Bugs Launches with Apple Wi-Fi Exploit ]
A hacker that takes control of a vulnerable router can:
"Portforward internal services (ports) to the router external facing side (a.k.a poking holes into your firewall and/or network)portforward the router web administration interface to the external facing side.Change the DNS server settings so that next time when the victim visits a legitimate banking site, they actually end up on malicious phishing site resembling the bank's site.Change the DNS server settings so that the next time when the victim updates Firefox extensions, they end up downloading evil code from the attacker's site.Reset or change the administrative credentials, the PPP settings or the IP settings for all interfaces.Reset/change the WiFi settings.Terminate the connection."
Petkov said it's difficult to approach individual router manufacturers about this issue because it's not a specific vulnerability affecting individual router models."[It's] a combination of design problems," he explained.
In the face of the GNUCITIZEN discovery, the US-CERT (Computer Emergency Readiness Team) recommends that users consider disabling UPnP functionality in routers.
Note: Disabling UPnP may cause applications that rely on UPnP to fail or operate with reduced functionality.