Re: Hijack IP Address using cable modem

[Patrick Maartense <patrick () MAARTENSE COM>]

No Even worse

HAcker from an other system somewhere in the internet does
1) iptraf for ARP

nmap target-network1-254 -p 21

does that nearby network bring ARPS for that range?

yes ?

Great:
ifconfig eth0:0-254 that range netmask 255.255.255.0

nmap target-network1-254 -p 21


Now the outbound interface REPLIES to those ARPS...
and is granted these additional ipadresses.

lets say my normal ipaddress is 195.202.128.158
on that PHYSICAL segment the ISP also assigne Class c for
62.80.123.0/28
62.80.124.0/28
62.80.125.0/28
195.202.128.0/28
195.202.129.0/28
195.202.130.0/28


Now it is 4 am in the morning, Joe and Jan Doe are in bed and have tunred of
their Computer

I dail in with my isdn modem from my notebook to my cost-by call isp
do pingsweep 62.80.123.0. 124.0, 125.0

see all those ARPS for the ips not know by the router ( for the last 20,30 mins)

configure my Cable Modem Box to have that COMPLETE class C on his iface

make the same pingsweep again
and now my box replies to these requests.
now i have these IP's

as i have leased 16 Addresses from that ISP i mode a proff of concept
using 2.4.2 kernel i configured my firewall to forward ALL request for port 80 (
except for my 16 addresses) AND ports 2000- 64k to my webserver port 8080
on that port i had a very nice welcome message that the ISP had misconfigured
their router. and the hotline number

I used that with one class C, called the to inform them with a kind reply to
reconfigure their network


got a NoNo..

informed local press and BugTraq...

If I can do that, everyone can..



Patrick Patterson wrote:

> -----BEGIN PGP SIGNED MESSAGE-----
>
> I think I see where Patrick was coming from with this:
>
> Victim turns on his computer, and gets an IP address
> Cracker, while sniffing the Cable segment notices that IP adress foo is
> assigned to MAC bar
> Cracker changes his own MAC address to bar, and brings up IP address foo on
> this new MAC address (some Ethernet cards have overwritable MAC addresses)
> Since both Cracker and Victim have the same MAC, Cracker get's all packets
> for Victims computer, and is able to impersonate victim.
>
> This is just a slightly more sophisticated IP Address Spoofing attack.... and
> I don't think it will work...
>
> > From what I know of Cablemodem networks, there are actually several parts.
>
> 1: The cable network - the 'Modem' talks to the Cable Company terminal
> equipment and ensures that you are a valid subscriber.
> 2: The IP Network - the routers keep track of which IP and MAC, is on which
> Cable Modem - thus making this attack unlikely to succeed....
>
> I haven't tested this, and might be horribly wrong, but I don't think so -
> this is one of those things that looks better in theory than in practice - Is
> anyone from @HOME or ATT around to confirm/deny what's I've written?
>
> On Wednesday 28 March 2001 09:09, Nick Summy wrote:
> > Now I hardly know anything about this subject, so correct me If im wrong,
> > but I have a few questions.
>
> <SNIP>
>
> - --
>
> Patrick Patterson                       Tel: +1 514 485-0789
> President, Chief Security Architect     Fax: +1 514 485-4737
> Carillon Information Security Inc.      E-Mail: ppatterson () carillonis com
>
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