Cyberguard and filtering of FTP on non-standard ports.

[LE CORVIC Y InfoEdpEtcDep <Yoann.Le-Corvic () socgen com>]

Hi all,

I have a question concerning filtering FTP on non standard ports.

I want to allow access to an FTP server behind a Cyberguard, but this server
is listening on high ports (for exemple 2021, 2020).
I wanted to know if it is possible to configure this firewall  to handle
"intelligent filtering" of FTP communication (PORT command monitoring or
PASV command pmonitoring), on ports other that 20 and 21. Any ideas would be
appreciated.

Thanks

-----Message d'origine-----
De : Paul D. Robertson [mailto:proberts () patriot net]
Envoyé : lundi 10 mars 2003 04:22
À : Chuck Swiger
Cc : 'firewall-wizards
Objet : Re: [fw-wiz] An article from Peter Tippett/TruSecure...


On Sun, 9 Mar 2003, Chuck Swiger wrote:

> Date: Sun, 09 Mar 2003 13:49:08 -0500
> From: Chuck Swiger <chuck () codefab com>
> To: 'firewall-wizards <firewall-wizards () honor icsalabs com>
> Subject: [fw-wiz] An article from Peter Tippett/TruSecure...

[Disclaimer:  I work for TruSecure, Dr. Tippett is both our CTO and the 
person I report directly to.  Since you didn't comment on the article, 
I'll take a swipe at the tradtional dogma as we tend to see it...]

>
http://www.globe.com/dailyglobe2/068/business/A_patch_for_IT_security_strate
gy+.shtml
> A brief excerpt:
>
> "For years, the focus of most security efforts has been centered on 
> identifying and then fixing vulnerabilities in technology.  The 
> prevailing belief is that if a hole is found in the IT armor of an 
> organization, it should be fixed immediately before it can be exploited 
> by some cyber-deviant.  While this approach sounds logical and 
> effective, it is actually the beginning of a vicious cycle that occupies 
> vast amounts of time and wastes several millions of corporate, 
> government, and consumer dollars every year."

The point that Peter's making is that chasing vulnerabilities just because 
they exist isn't efficient, nor really achievable.  There were ~2200-2400 
new vulnerabilites announced last year, and as near as I can tell, 
between 1 and 2% of those new vulnerabilities got exploited at real
companies.

That means that if you spent time patching say an applicable 70% of those 
vulnerabilities, then 68% of that time was wasted.  

It's purely a risk funciton- and if you have good data on which small 
percentage of new vulnerabilities are going to be exploited and which ones 
have historically been exploited, then you can reduce your risk by 
about the same ammount by patching let's say 5% of those vulnerabilities 
instead of every one.  

That saves you 65% of the maintenance, fixes, "patch breaks things" and all 
the associated change control stuff.  If you pay folks overtime, or 
give comp. time for staying late to patch, those can go down significantly 
too- *especially* if you have protections in place that limit damage from a 
particular vector for long enough between vulnerability disclosure, 
exploit coding and a normal maintenance cycle.

Proactive security beats reactive security every time.  Patch upon 
vulnerability release is reactive.  Things like firewalls and conservative 
machine configuration can reduce patching levels for attacks from likely 
vectors without negatively changing an organization's risk profile.  
Indeed, there's an argument that if people spend more time on the likely 
vulnerabilities, they'll be able to better-protect an organization than if 
they spend time patching every possible vulnerability.

I've got excellent data for widespread worms like SQL/Slammer and NIMDA, 
and a good feel for the results of target of choice attacks.  That risks 
putting this too far into the "sounds like a commercial" mode though, so 
I'll just leave it at "smart risk-based patching beats blanket patching 
for effieciency with little measurable change in risk."


Paul
----------------------------------------------------------------------------
-
Paul D. Robertson      "My statements in this message are personal opinions
proberts () patriot net      which may have no basis whatsoever in fact."
probertson () trusecure com Director of Risk Assessment TruSecure Corporation

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