Re: Small TCP packets == very large overhead == DoS?

From: Eric Vyncke (evynckeat_private)
Date: Mon Jul 09 2001 - 08:20:50 PDT

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    Darren,
    
    Interesting email...
    
    If the attack is done through bad client specifying a ultra small MSS, at 
    least, the server should be able to track them. As doing IP spoofing with 
    TCP is difficult if the ISN are random enough.
    
    If the attack is done through generated ICMP unreachable cannot fragment 
    (mimicking the PMTUD process), well, the attacker needs to be on the path 
    to be able to include the failed IP packet (mainly for TCP ports). And if 
    the attacker is on the path, I'm pretty sure that he/she could do more 
    damage anyway.
    
    Having said this, I'll go to my web servers and check what their smallest 
    MSS is ;-)
    
    Just my still falling (!) 0.01 EUR
    
    -eric
    



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