Re: OpenSSH is a good choice?

[Ben Hawkes <ben.hawkes () paradise net nz>]

On Thu, Dec 23, 2004 at 12:43:31AM -0600, Ron DuFresne wrote:
> My thoughts on this have centered on the point that there are too many
> decent scanning and banner grabbing tools out there to make botuse port
> assingments off the default any much good at obscuring the service.
>
> We are lucky in that most the coded sploits and POCs tend to be cheap in
> that they tend to look for specifics in a very narrowly focused tunnel.
> The potentials for something being crafted that is much more insidiously
> inventive in determing attack vectors that might be non-norm are there.
> And beaucse they remain at this time 'potential' should not be a reason or
> rationale to try and place minimally effective or incomplete controls in
> the security layers one uses.  The IT community has been repeatedly bitten
> by doing less then they know better to do due to the potential of
> something not yet unleashed, say 1988 for example.

There needs to be some differentiation between worms and exploits here.
In the case of a single attacker specifically targeting a machine, then
yes, I agree that a non-standard port configuration is not going to
help due to such "insidiously inventive" tools as nmap and its -sV.
However a non-standard port does help in the general case when it comes
to a worm. 

The reason that we have not seen a worm search for non-standard 
configurations is not so much a lack of ingenuity by the authors, 
but more of a realisation that the time spent on scanning each target 
is better spent looking for other potentially vulnerable hosts with a 
standard port configuration. That is to say, searching each potential
host for non-standard ports is inefficient and would likely inhibit the
spread of such a worm.

I don't have any figures to support this claim, but its hard to imagine
the percentage of non-standard port configurations for any service on
the internet being high enough to be an attractive target for a worm. In
the end, running a service on a non-standard port at this point in time 
is a useful part of a layered security approach, if only to inhibit
worms.

-- 
Ben Hawkes
pie.sf.net
(fiver)
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