A backdoor found in firmware used in several D-Link routers could allow an attacker to change a device's settings, a serious security problem that could be used for surveillance. Craig Heffner, a vulnerability researcher with Tactical Network Solutions who specializes in wireless and embedded systems, found the vulnerability. The affected models likely include D-Link's DIR-100, DI-524, DI-524UP, DI-604S, DI-604UP, DI-604+, TM-G5240 and possibly the DIR-615. The same firmware is also used in the BRL-04UR and BRL-04CW routers made by Planex, Heffner wrote. D-Link officials could be immediately reached for comment on Monday.