Back in October, it was discovered that many D-Link wireless access points had a backdoor that would grant administrative access to the management interface. The backdoor was simply a user agent—specifically “xmlset_roodkcableoj28840ybtide”—that was hard coded in the device firmware to skip the authentication check for proper administrative credentials, no username or password required.
A user agent is the identity claimed by a browser (or other client utility) when communicating with a service. For example, the user agent of Chrome 32.0.1667.0 is “Mozilla/5.0 (Windows NT 6.2; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/32.0.1667.0 Safari/537.36.”
The suspicious D-Link user agent might have been created for testing, debugging, and maintenance and then was overlooked, or it could have been planted maliciously by a programmer to take advantage of customers later. In either case, it is a serious problem that owners of D-Link devices need to address.
The fix for this D-Link issue is to upgrade the firmware on the wireless access point. D-Link claims to have released updated firmware for the affected models to resolve this issue.
But what other problems might be lurking in the firmware that are yet to be discovered? This is a question every wireless access point owner should consider.
Can you trust the firmware from a closed-source vendor? Maybe, maybe not. To be sure that your device’s firmware does not contain backdoors or other security problems, consider running one of the many excellent open-source firmware alternatives.
Some of the more well-known options are DD-WRT, Tomato, OpenWRT, m0n0wall, pfSense, and Vyatta. Be sure to visit their sites to view the list of compatible devices and how-to guides on replacing your wireless access point’s firmware.
I run DD-WRT on all of my wireless devices, and I’ve never considered reverting back to vendor firmware.