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Thread: Nmap running very slowly

  1. #1
    Just burned his ISO
    Join Date
    Sep 2011

    Default Nmap running very slowly

    Hi all, just downloaded backtrack for the first time, im new to the whole scene. Came to trying out an Nmap scan on a metasploitable VM, and a tcp scan using the default 100 ports of one host takes 2 minutes to complete. The book im following suggested scanning all ports rather than just the default 1000, and after 5 or so minutes i checked on the progress and nmap informed me that there was two HOURS left before the scan was complete.

    From everything ive seen so far, im pretty sure that this should not be the case, so i was wondering if some1 could help me troubleshoot a little.

    Im running Backtrack 5 Gnome 32 bit on VMWare Player, scanning a Metasploitable VM also in VMWare player. The command i used was as follows:

    nmap –sT -p- -PN IP Address

    Thanks in advance!

  2. #2
    Moderator g0tmi1k's Avatar
    Join Date
    Feb 2010

    Default Re: Nmap running very slowly

    Take the time to read up on nmap ("man nmap" is a good place to start) - there are methods of speeding it up. However they do have their downsides. (You'll need to do the research yourself as there is a fair bit & its already been covered in depth before).
    Dont forget to look at alternative programs - current personal favourite is unicornscan.
    Have you...g0tmi1k?

  3. #3
    My life is this forum thorin's Avatar
    Join Date
    Jan 2010

    Default Re: Nmap running very slowly

    As g0tmi1k suggested there are many ways to speed things up, consider checking out: or more specifically

    Also keep in mind that you're working against a VM not a real machine.

    While unicornscan is indeed an alternative it it's also very out-of-date (likely because Jack died in 2009).
    I'm a compulsive post editor, you might wanna wait until my post has been online for 5-10 mins before quoting it as it will likely change.

    I know I seem harsh in some of my replies. SORRY! But if you're doing something illegal or posting something that seems to be obvious BS I'm going to call you on it.

  4. #4
    Just burned his ISO
    Join Date
    Sep 2011

    Default Re: Nmap running very slowly

    There might be the following issuer, check if you are scanning a firewalled hosts, this might take up to hours to scan all ports even on LAN, as firewalls rejects packets and slows the scanning.

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