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Bonjour, Joel!

Joel CARNAT wrote:
> I spend the last two days at "Microsoft Security Days" in Paris while I
> was spammed with "M$ does it", "M$ is great", yadda yadda... When I put
> the commercial aspect away, there ISA server 2004 looks pretty nice.
>   
Microsoft products tend, indeed to *LOOK* pretty nice. It gets ugly when 
you start hitting security issues due to core OS design and other 
things... But, grated, it *LOOKS* nice.
> To sum up, it is a firewall that can deal with network flow at
> application level (aka ISO layer 7) - that is, it can block data flow if an
> HTTP/SMTP/... command is known to be bad (too long, attack signature, ...).
>   
Not that I can see, directly, on te NetBSD software list. But you could 
build one on a dual network interfaced host which doesn't forward IP 
packages, and relevant proxy packages. You could install SQUID HTTP 
proxy, and SMTPD SMTP proxy which would do the 2 you mention above.
> My question is, using NetBSD ;), what is the way to validate network flow
> at level7 ? Is it postfix that can kill a session (for eg) if the HELO
> command gets more than "64" chars ? Is it squid that can terminate a
> session if it see URL patterned like "GET blabla.php?vars=DOSme\n\n\n\n"
> ? How do we do this is the free world (didn't find anything on
> google|freshmeat - but I may not have use the right search pattern).
>   
Application level firewalls require heavy application knowledge... 
usually very specific code. Luckily enough, there are these packages 
(see above). Beyond that, there are commercial products... :)

Gilles.

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