Security experts report a cross-platform flaw in the Universal Plug and Play (UPnP) protocol and Flash can be abused to take over your router and redirect you to malicious websites:
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.