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Thread: Nmap filtered ports from BT4 virtual machine

  1. #1
    Just burned his ISO
    Join Date
    Jun 2010

    Default Nmap filtered ports from BT4 virtual machine

    I am doing a pentest on a friend's server, and from my main OS (ubuntu), nmap shows a few open ports, but from a Backtrack 4 I have in a virtual machine (virtualbox), I get the same ports filtered.

    Does someone knows why this happens and if it can be "fixed"?

  2. #2
    Junior Member
    Join Date
    Nov 2010

    Default Respuesta: Nmap filtered ports from BT4 virtual machine

    If the ports appears open, the ports are in use or iptables bad configured.
    In your case you give very less information. My answer is i dont know.
    Did you run nmap from VM and Ub at same time? What scan?

  3. #3
    Super Moderator Archangel-Amael's Avatar
    Join Date
    Jan 2010

    Default Re: Respuesta: Nmap filtered ports from BT4 virtual machine

    Just because a port is open does not mean that it is not filtered.
    It would do you well to look into the nmap documentation.
    To be successful here you should read all of the following.
    If you are new to Back|Track
    Back|Track Wiki
    Failure to do so will probably get your threads deleted or worse.

  4. #4
    Just burned his ISO
    Join Date
    Jun 2010

    Default Re: Nmap filtered ports from BT4 virtual machine

    I will try explaining more my situation.

    As I understand, a simple port scanning would first send a SYN probe packet, then if it receives a packet with SYN and ACK flags, the port should be open but if it receives a RST/ACK packet then the port is close. Now, filtered ports don't receive neither a SYN/ACK or a RST/ACK packet back after the first SYN packet is sent (not sure if this is correct), and what cause this most of the time is a firewall on the other end.

    So, I am doing a simple scan on the target server with

    nmap <HOST> -v
    From my main OS (ubuntu 10.04), I get the port 80 open, which means I am receiving a SYN/ACK packet. But when I try the same scan from BT4 (installed in a Virtualbox VM), the result shows the same port as filtered, so nmap is not receiving a SYN/ACK packet as response.

    On the BT4 virtual machine, I connect to the internet using Network Adapter > Attached to > NAT, I just run "/etc/init.d/networking start" and it works fine, I never configured anything else.

    I was wondering if I should configure something to get nmap working on the virtual machine as it's working on the main OS, I can't figure out what could be causing this and I couldn't find any info on google about this "problem".

    Btw, I am not running the scans at the same time on Ubuntu and BT4.

  5. #5
    Junior Member roybatty's Avatar
    Join Date
    Jan 2010
    Tannhauser Gate

    Default Re: Nmap filtered ports from BT4 virtual machine

    You don't understand the implications of using Virtualbox NAT. Use bridged networking instead.
    Last edited by roybatty; 12-25-2010 at 05:07 PM.
    I've seen things you people wouldn't believe.

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