This posting on Bugtraq clearly demonstrates the stupidity of relying on obscurity to protect a default backdoor in internet equipment.

I was playing with a
Dynalink RTA 230 (http://www.dynalink.co.nz/products/rta230.htm), a linux
based mips-cored adsl router. Looking at embedded linux system, i've found something like a backdoor:

# cat /etc/passwd
admin:xxxxx(obscured)xxxxx:0:0:Administrator:/:/bin/sh
userNotUsed:YNf8oSCwK/0/Y:0:0:Technical Support:/:/bin/sh

Then forced the pass with John:

root@sbongaz:~/john-1.6/run# ./john passwd -show
userNotUsed:userNotU:0:0:Technical Support:/:/bin/sh

the first user is the administration account also used by http config center;
the second entry in passwd is not visible or modificable from the user config center. Luckly access to the http config center and telnet shell is blocked (not enabled by default) from outside the lan.

When will they ever learn that there is no substitute for real security ... and you can't hide backdoors.