decoyed IPs

From: kahleong_fong (kahleong_fongat_private)
Date: Wed Jul 09 2003 - 02:22:25 PDT

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    hi, 
    I am investigating a set of IPs NMAP_TCP_PING which
    appeared to be using some decoyed IPs. However they
    are all valid IPs. Most of them are from the same ISP
    and the only port that is opened is port 80 on their
    site.
    
    I need to know how am I going to narrow down to which
    are the probable ones. Afew of these IPs belongs to
    ISP, however not listed in the dns, these I suspected
    to be proxy. 
    
    One thing I noted, I thought they used a filtering
    router to allow port 80 to come in, however it would
    appear they  are using more than a filtering router.
    This filtering device appeared to be adaptive or
    reactive. It allowed you to connect to port 80 of
    these IPs, however dropped the connection after issued
    of "GET /". Then refused or reset the connection on
    second attempt onwards using the same src IP connected
    from. It somehow reset what it learned the next day
    and allow connection again, and refused connections
    after the first attempt.
    
    I am not familiar with ISP perimeter setups. Anyone
    can give me an idea to what they are using? 
    
    Thanks in advance.
    regards.
    
    
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