Updated The worm called “The Moon”, which began spreading between Linksys home broadband kit last week, has been confirmed as a problem with the devices' HNAP1 implementation, and an exploit has been made public.
Possible vulnerable devices include the Linksys E4200, E3200, E3000, E2500, E2100L, E2000, E1550, E1500, E1200, E1000 and E900, according to the SANS Institute, which first spotted the worm in the wild. The SANS Institute also notes that vulnerability depends on firmware revision.
Unfortunately, some of the devices in the list are no longer supported, so users can't get new firmware (for example, as El Reg noted last week, the E1000 is on the no-longer-supported list).
HNAP – the Home Network Administration Protocol – was created by Pure Networks and acquired by Cisco, and provides admin access to HNAP-enabled kit. As the SANS Institute's Rob VandenBrink writes here, “the irony of someone 'in the biz' deciding in 2007 that we need yet another clear-text network management protocol does not escape me”. ®
Updated to add
Linksys has contacted The Register with the following statement: "Linksys is aware of the malware called “The Moon” that has affected select older Linksys E-Series routers and select older Wireless-N access points and routers. The exploit to bypass the admin authentication used by the worm only works when the Remote Management Access feature is enabled.
"Linksys ships these products with the Remote Management Access feature turned off by default. Customers who have not enabled the Remote Management Access feature are not susceptible to this specific malware. Customers who have enabled the Remote Management Access feature can prevent further vulnerability to their network, by disabling the Remote Management Access feature and rebooting their router to remove the installed malware.
"Linksys will be working on the affected products with a firmware fix that is planned to be posted on our website in the coming weeks." ®