Re: Some new SSH exploit script?

From: Thor (Hammer of God) (thor@hammerofgod.com)
Date: Wed Jun 07 2006 - 14:49:21 EDT


 
> Changing the port number, is akin, to hiding the door, because your
> afraid of the lock installed in it. It only raises the bar to the
> special olympics level.
>
> I believe in security in-depth, but this depth is so superficial, I
> really don't think it's worth it.
>

No, it's akin to hiding the door in _addition_ to having strong locks on it.
This subject comes up here from time to time, and it basically always comes
down to someone saying "it's so trivial that it doesn't matter" and others
saying "if it helps at all, even if only slightly, then it's a good thing."

I number myself among the latter group- if it raises your fruit higher than
the guy next to you, then go for it. Changing default listening ports
immediately obviates you from standard/worm/kiddie traffic. That, in itself
is a good enough reason for me.

We had this discussion over on the ISA list about RDP several months back.
After that thread, I hosted terminal services and SQL on 2 boxes: one on
3389/1433, the other on 53343/43343 respectively for Feb, March and part of
April. There were something like 45,000 failed RDP logon attemps on 3389,
and not a single logon attempt (other than from me) on 53343. The SQL
numbers were almost 200,000 on 1433, and something like 10 on 43343. I was
actually pretty surprised to see the 10. (I've got the actual numbers on
the box itself, I might bring it up and get the actual figures if I get
time).

You can speculate about port-scanning worms, "intelligent" viruses, etc all
you want, but they're just not being written (yet). Moving my RDP listener
to 53343 prevented over 45,000 logon attempts. To me, that is not a
superficial security-in-depth mechanism. There are a million different
things that *could* have been done, but they just weren't.

I'll continue to host RDP on an alternate port because it provides some
value, albeit small, to my security in depth strategy.

I also continue to find value in "source port" firewall rules where only
connections to services initiated from a particular source port are allowed.
Others have said that practice is also just "security through obscurity" yet
I think it is a good idea, and it works for me. I use this method to help
protect access to my production servers for remote RDP access - RDP listens
on an alternate port, and my ISA server only allows the connection when made
from a specific source port (I actually use a small range of source ports) -
there has never even been a connection attempt made (other than from me.)

Given actual data I have collected, I'll continue to use this method as
well.

t

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