Flash attack could take over your router

by Robert McMillan

January 15, 2008 —

Security researchers have released code showing how a pair of widely used technologies
could be misused to take control of a victim's Web browsing experience.

The code, published
over the weekend by researchers Adrian Pastor and Petko Petkov, exploits
features in two technologies: The Universal Plug and Play (UPnP) protocol, which
is used by many operating systems to make it easier for them to work with devices
on a network; and Adobe Systems' Flash multimedia software.

By tricking a victim into viewing a malicious Flash file, an attacker could
use UPnP to change the primary DNS (Domain Name System) server used by the router
to find other computers on the Internet. This would give the attacker a virtually
undetectable way to redirect the victim to fake Web sites. For example, a victim
with a compromised router could be taken to the attacker's Web server, even
if he typed Citibank.com directly into the Web browser navigation bar.

"The most malicious of all malicious things is to change the primary DNS
server," the researchers wrote. "That will effectively turn the router
and the network it controls into a zombie which the attacker can take advantage
of whenever they feel like it."

Because so many routers support UPnP, the researchers believe that "ninety
nine percent of home routers are vulnerable to this attack."

In fact, many other types of UPnP devices, such as printers, digital entertainment
systems and cameras are also potentially at risk, they added in a Frequently
Asked Questions Web page explaining their research.

The attack is particularly worrisome because it is cross-platform -- any operating
system that supports Flash is susceptible -- and because it is based on features
of UPnP and Flash, not bugs that could be easily fixed by Adobe or the router
vendors.

Users could avoid this attack by turning UPnP off on their routers, where it
is normally enabled by default, but this would cause a variety of popular applications,
such as IM (instant-message) software, games and Skype, to break and require
manual configuration on the router.

Adobe could make changes to Flash to mitigate the problem, but attackers could
most likely also launch this attack using another technique, known as DNS pinning,
said Aviv Raff, a researcher who has also blogged
about the attack.

"This is a critical issue," he said in an IM interview. "People
should turn off UPnP in their devices, and vendors should put UPnP disabled
by default in the devices they deliver."

Although this could make life difficult for nontechnical users, Raff believes
it would be worth the effort. "It's better than having your traffic owned
by malicious people," he said.

However, another security expert said that turning off UPnP would be overkill,
considering that online criminals have not even begun using this attack. "Look...
if you get hit by a meteor, it's devastating," said Roger Thompson, chief
research officer with Grisoft, via IM. "But no one goes around building
meteor shelters."

IDG News Service