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Re: OpenSSH is a good choice?
From: dk <dk () pwarchitects com>
Date: Thu, 23 Dec 2004 20:38:28 -0600

Willem Koenings wrote:
On Wed, 22 Dec 2004 02:40:25 -0600 (CST), Ron DuFresne
<dufresne () winternet com> wrote:

I'd disagree in that the tools are getting to be well enough defined that
we are all targets.  Best game is to restrict who has access to the ports
being served whenever possible, openssh has a history that makes this a
good service to limit this way.  Little need to hide what's not openly
allowed to all.

take a recent phpBB worm Santy for an example. worm seaches
automatically targets via google - it searches
viewtopic.php. if, for an example, you change that file name to
something else (and also all the referrings inside the phpBB so that
everything still works), then Santy does not find you phpBB as a
target. this is only an illustration to my point.

(Hi there. sorry for butting in.)

This concept does work for a little bit... As it is exactly what I did: using the same highlight hole to rename viewtopic.php to viewtopic1.php for a friend who was unreachable during the worms first hit. But it also took me only a few minutes messing with the query that the worm used to mod it to make /some/ schemes like this into account on the next google indexing - and my current perl 5killz are not uber. ;-/ I just mention it because non-std mods to anything can breed a different sort of complacently. In the end it's the same ole' game I guess.

i wrote my post because you say "the non std port advice is not worth
much". i have lot of cases, when non standard configuration reduces
first impact greatly. of course you shouldn't rely only to non
standard ports/configuration, but it is not totally worthless - it
often helps you a lot.

I too agree that it's not worthless for certain usages, especially as you mention: on first impact. But depending on context it _can_ create more burden on the admin later when you must recall what non-standard changes /you/ made to the application or source package when upgrade time comes around. Files may not be patched/removed due to name changes and could be left available for future exploits. These custom changes may also open you to other issues in the future... like putting ssh on a high port that turns into a popular p2p port in a years time and it hammers your logs or some such. <shrug>

Anyway - In this specific case, if the OP wanted to further restrict ssh from pre-auth bugs a system like fwknop[1] or SAdoor[2] would work better to open the std port 22 (or what ever) than simple port knocking.

[1] http://www.cipherdyne.org/fwknop/
[2] http://cmn.listprojects.darklab.org/

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