Click picture for more....

Is there any way to keep someone from plugging in a
console port and using password recovery procedure to
get into a router? for instance if you have a router
at a remote site and someone decides they want to
alter your config etc. what could stop them? (besides
a huge padlock ?)

Not a problem.. find your nearest router with an ISDN BRI or even better,
PRI port.  Boot this router up, and enable the ISDN port.  Insert one end of
an RJ-45 cable into this ISDN, making sure the other end is FAR away from
your switches.  Then go around your rack of routers you would like to
secure, and carefully insert the other end of the RJ-45 cable into the
appropriate router's console port.

Please note to pay attention to not ignore the happenings, as there may be a
little smoke, and the RJ45 cable may warm up quickly.  If this occurs,
quickly power off the ISDN router, and if required, apply fire extinguisher.
(haha, it's not that bad, but couldn't resist).

Voila.. permanently secure console port.

Of course, please reference your service contract with Cisco Systems prior
to applying this procedure, to see something about maliscious misconduct
effecting your warranty.

---------
This is a comical reply.  Don't try this at home, kids.  We are highly
trained professionals.

Regards,
  Trevor Corness, CCNA MCSE MCP+I CiscoConsoleSecurityAssociate.

Click picture for more....