spoofed packets to RFC 1918 addresses

From: Dirk Koopman (djkat_private)
Date: Wed Jun 26 2002 - 08:48:51 PDT

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    There seems to be a "tool" about, which is somehow able to
    detect valid rfc1918 addresses behind a NATed firewall and is spoofing
    from addresses using random (usually non-existant) addresses from the
    class C on the internet side of that firewall.
    
    It isn't doing them any good as the packets are being dumped before they
    get to the 'visible' class C (as I am making sure that packets from that
    class C emanate only from the interface attached to that class C). 
    
    However, I am interested to know:
    
    a) how the attackers are able to "guess" correct (ie existing) rfc1918
    addresses as, AFAIK, these are not being leaked thru the firewall.  
    
    b) how these packets are getting to me in the first place as they don't
    seem to be source routed. 
    
    c) which "tool" is doing this anyway.
    
    Regards
    
    Dirk Koopman
    -- 
    Please Note: Some Quantum Physics Theories Suggest That When the 
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