Re: SYN Proxy

[Daniel Cid <daniel.cid () sourcefire com>]

Your Linux box running snort in inline mode can't be considered a 
firewall. By the default, snort-inline allows everything and only block 
what it detects as "wrong". You BSD firewall should block everything and 
only allow what is necessary on your network.
It's two different devices doing different things. Do not expect your 
IDS (snort inline is basically an IDS with a blocking response) to do what
your firewall should be doing.

Daniel

Xavier Cabrera wrote:

> Hello:
>
> Thanks for all your answers. Wel i think too the best aproach for this 
> is doing on iptables like Will say.. but if we really want a IPS with 
> snort maybe we can start to think on that solution. Maybe people of 
> sourcefire can plant this solution for future releases.
>
> If snort in future can handle the connections with syn proxy or (seudo 
> syn proxy) validating the real one's before they can pass can start to 
> think in the best IPS of the World
>
> Well, i have to continue with my two boxes.... Like Matt say... right 
> now i have a Linux-Snorted behind a BSD.... and that is not 
> elegant.... A firewall behind another one?
>
>
> Regards
>
> Xavier Cabrera.
>
>
> Will Metcalf wrote:
>
> > I could think of a way to do this, it probably wouldn't be very clean
> > and would more than likely require an ip stack to be loaded on your
> > inline box.
> >
> > This is really something that should be handled in netfilter rather
> > than in snort-inline.  If packets make it to the queue and you have a
> > lot of spoofed packets your DoS isn't going to be on the end host your
> > trying to protect, it's going to be your inline box dealing with all
> > the damn context switching between user space and kernel space.
> >
> > Regards,
> >
> > Will
> >
> > On 7/19/05, Matt Kettler <mkettler () evi-inc com> wrote:
> >  
> >
> > > Xavier Cabrera wrote:
> > >   
> > >
> > > > Anyone know how snort can work like a Syn Proxy in inline mode?
> > > >     
> > >
> > > Not that I'm aware of.. Ultimately I think you'll have to do this in 
> > > two stages,
> > > something like this:
> > >
> > > PC -> syn proxy -> snort inline -> Internet
> > >
> > > You might be able to wrap it all up on the same box by using two 
> > > interfaces and
> > > have the proxy tool running on the inside interface, and then inline 
> > > snort on
> > > the outside.
> > >
> > >
> > > Something like this:
> > >
> > > inside interface ->syn proxy -> OS routing -> snort inline -> 
> > > outside interface
> > >
> > >
> > >
> > > but I'm not up-to-speed on all the syn proxy tools out there, or 
> > > snort's current
> > > inline support.
> > >
> > >
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>
>
>
>
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