Re: TCP Resets

["Josh Berry" <josh.berry () netschematics com>]

I currently use snort-inline at the perimeter to do inline blocking.  I
was just trying to assess the value (if there is any) of using regular
snort ids with tcp-resets on the internal side of the network.

> twig les wrote:
> > --- Josh Berry <josh.berry () netschematics com> wrote:
> >
> > > I am trying to assess the value of using TCP Resets on Exploit
> > > attacks over TCP such as Blaster and Code Red.  It seems as though
> > > trying to reset these types of connections will just double the
> > > amount of network traffic while not stopping the exploit.  Won't
> > > the reset reach the machine too late as the IDS is reacting just
> > > after the connection is seen?
>
> > That is a band-aid.  The core problem is the infected host. Aside
> > from double the traffic it does nothing to fix the core problem, just
> > the symptom.  If snort is not inline it may get bogged down enough to
> > let a payload pass anyway.
>
> If you issue an RST (assuming inline):
> * generates return traffic,
> * fakes most scanners into believing port is closed,
> * attacker can rapidly continue their attack/scan
>
> If you do not issue an RST, but silently drop:
> * no return traffic,
> * attacker must wait for timeout,
> * scanners assume the port is "filtered"
>
> Inline will indeed not work exactly as expected, the above rules apply
> to strictly inline devices (firewall, iptables, etc).
>
> Jeff
>
>
>
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Thanks,
Josh Berry, CISSP
CTO, VP of Product Development
LinkNet-Solutions
469-831-8543
josh.berry () linknet-solutions com



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