Re: Using a Compromised Router to Capture Network Traffic

["Fabio Pietrosanti (naif)" <naif () blackhats it>]

On Mon, Jul 15, 2002 at 10:43:49AM -0800, Penetration Testing wrote:
> Hi all.
>
> I have recently completed some experimentation into using a captured
> router to sniff network traffic on a remote network.  This is in the same
> vein as Gauis' article in Phrack 56 (Things to do in cisco land when you
> are dead).
>
> I have tried to build on Gauis' work in that I terminated the GRE tunnel
> on a Cisco router instead of a *nix machine.  I explored a couple of
> possible scenarios for this, the net result being that it is possible to
> remotely capture (bi-directional) network traffic using NO customised
> tools; all that is required is one cisco router with vanilla IOS, and a
> machine that can run snoop or tcpdump.

Why having a "so complex" infrastructure ?

All you need is linux 2.4.X kernel with netfilter and GRE support and the following tools:

- iptables
- iproute2
- any sniffing/hijacking tools ( ettercap, dsniff, hunt, ethereal )

Using this configuration you can do whatever you want:

- create funny policy routing rules
- intercept traffic
- hijack traffic
- decrement TTL and manipulate traffic in many way
- insert NAT rules to eventually bypass firewall

and you don't need to have a cisco router neither to have to cope with GRE
encapsulation :)

Using a cisco router for hacking purpose is crazy, use linux! :)


Regards


--

Fabio Pietrosanti ( naif )
E-mail: naif () blackhats it - naif () sikurezza org
PGP Key (DSS) http://naif.itapac.net/naif.asc
--
 "Hacking is the future of security research" R.Power, CSI 
Free advertising: www.openbsd.org Multiplatform Ultra-secure OS

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