Fwd: FW: session-hijacking is still available?

["crawford charles" <biv0uac17 () hotmail com>]

I had thought that the original thesis was that for older TCP 
implementations, an attacker could make a reasonable guess about the 
starting sequence number of a new TCP session, given the sequence numbers 
for a previous one (i.e. one he could observe).  Then he would attempt to 
hijack a subsequent TCP session that he might not be able to observe, but 
could predict or infer.  Newer TCP implementations start the sequence number 
for each new session at a random value, and increment from there.  But 
sequence numbers still have to increment monotonically (presumably by the 
number of bytes in each TCP PDU).

If an attacker can monitor the link between the client and server of a TCP 
session in real-time, and can inject packets "fast enough", he can still 
hijack a session, as the sequence numbers for the hijacked session will be 
directly observable.  The counter to this level of attack is to encrypt, 
preferably at the IP layer (one can still encrypt at the TCP layer, 
preventing the hijacker from doing anything "useful", but the victim session 
 is still disrupted -- DoS).



> -----Original Message-----

From: SB CH [mailto:chulmin2 () hotmail com]
Sent: Thursday, April 03, 2003 8:44 PM
To: security-basics () securityfocus com
Subject: session-hijacking is still available?


Hello, all.

if attacker can do session hijacking, he can know the seq number change,
ack seq number change something like that.
But I have heard that modern system like linux kernel 2.4.x or openbsd
produce almost random seq number, so session hijacking is almost impossible
thesedays.

is it true or not?
anyone still can session hijacking using session hijacking program like
hunt?

Thanks in advance.


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