ARP Spoofing and Routing

From: Kyle Starkey (kstarkey_at_siegeworks.com)
Date: 09/30/05

  • Next message: spoofy root: "Detection of promiscuous devices that don't have an IP?"
    To: <pen-test@securityfocus.com>
    Date: Fri, 30 Sep 2005 12:33:26 -0600
    
    

    Folks..
    I was on site yesterday at a client doing some pen-test type work and
    thought I might play around with some arpspoofing and see what I could
    gather. I ran into a couple of problem and thought you all might have the
    solution.

    What I was trying to do was arpspoof a server so that I could intercept any
    authentication requests that were made to it and grab passwds or hashes to
    find some user accts. I was using the Auditors Toolkit bootable CD and the
    arpspoof worked great. A tcpdump of the eth0 int when the spoof started
    showed that I was getting all the traffic that should have been destined for
    this server (hosts and server and myself were all in the same bcast seg
    btw). However I was not running any deamons (ftp, samba, telnet, etc) to
    answer these requests and as such was only seeing part of the conversation
    and couldn't complete the connection to get the full auth request. So what
    I need to know is how I go about sending packets that were destined for the
    server originally to the actual server after I have had my
    tcpdump/dsniff/etc doing the packet capture and filter. My ideas are as
    follows and I could use some responses about them or OTHER ways I can
    accomplish this...

    1) routed routing traffic to the original host with a static ARP entry in my
    host for the server I am spoofing so I don't spoof myself

    2) some kind of proxy server that will capture and forward traffic based on
    the dest addr of the packet and again a static arp entry for the host being
    spoofed so we don't spoof ourselves

    3) load ftpd, samba, telnet, to answer these requests, even if we are
    denying auth people will still pass user credentials in an attempt to login,
    after the arpspoof has happened...

    4) some other already built tool that I have never heard of and should learn
    to use...

    If this makes no sense please feel free to flame me and call me an idiot,
    but its been a long week and the coffee aint helping...

    -K

    Kyle R. Starkey
    Senior Security Consultant
    CISSP # 31718
    Siegeworks LLC
    Email: kstarkey@siegeworks.com
    Cell: 435-962-8986

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