[Full-disclosure] info on ip spoofing please

[Valdis.Kletnieks at vt.edu]

On Tue, 11 Apr 2006 21:54:50 BST, Ian stuart Turnbull said:
> Excellent response Brendon. Thanks heaps.
> I was reading the infamous Markoff / Tsutomu Shimomura attack at 

That was *Mitnick*, not Markoff - Markoff wrote a book or 3 about it later.

> http://www.totse.com/en/hack/hack_attack/hacker03.html
> 
> and I guess I assumed that as they did not know each other personally then 
> Markoff must have found a way to locate 2 computers conversing with each 
> other randomly? Perhaps this assumption was not correct?
> Though from the test it appears Markoff DID find a way of doing this - ie, 
> finding 2 computers talking to each other NOT on his own LAN / network???

Well, at that time, it was a pretty good guess that if you found hostnames
george.site.dom, paul.site.dom, john.site.dom, and ringo.site.dom, and all 4
had rsh enabled, that there was a lot of rsh traffic between them, and likely
a .rhost trust between them so you wouldn't need a password....

And what Mitnick's attack did *wasnt* finding 2 computers *talking*.
In fact, the attack relied on finding a trusted computer *not* talking (or
making it not talk).

What he did was:

1) Bash george.site.dom over the head with SYN packets to make it STFU.
2) Send paul.site.dom a forged SYN packet claiming to be from george.
3) Paul sends a syn/ack to george, who can't send an RST because it's STFU.
4) send a forged ACK for the syn/ack claiming to be from george.
5) Send the rest of the TCP datastream.

The only tough part is knowing what ISN will be on the syn/ack so you can
ack it properly - and in that day, just poking its 'finger' port or something,
noting *that* ISN, and adding 32K or similar constant was almost guaranteed to work.
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