North American Network Operators Group

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  • From: Hank Nussbacher
  • Date: Sun Apr 30 02:31:06 2000

At 15:06 28/04/00 -0600, Alec H. Peterson wrote:
>Paul Froutan wrote:
>> I don't think you can.  However, I use TACACS on all my switches and
>> routers.  From what I know, TACACS passwords are encrypted using the key on
>> your network devices and the TACACS server.  So, that, in combination with
>> a private management LAN not accessible by your customers should lock down
>> your network pretty effectively.  Any comments?
>Using TACACS+ with some sort of one-time-passwording works very well.

TACACS encryption won't help if you follow the Cisco Essential IOS Features
(v 2.82 - Feb 18, 2000).  On page 45 they discuss router command auditing
and recommend:

aaa accounting command 15 start-stop tacacs+

Unfortunately, this will log in your syslog the password commands in
cleartext.  You would have to be sure that the Unix/NT system you are
logging all Cisco commands to is as secure as your router.  How many of you
run ISS/Cybercop/Netrecon scans every week on your logging servers to be
sure they are secure?

"aaa accounting command 15 start-stop tacacs+" can be considered an
unintentional backdoor for many.

I informed the Cisco authors when it was published to issue a document patch.


>Alec H. Peterson - [email protected]
>Staff Scientist
>CenterGate Research Group -
>"Technology so advanced, even _we_ don't understand it!"