Random UDP port open.

This is a discussion on Random UDP port open. within the Tech Board forums, part of the Community Boards category; I ran a port scan on my machine, I fount that everything is how I like it - save for ...

  1. #1
    Unregistered User Yarin's Avatar
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    Random UDP port open.

    I ran a port scan on my machine, I fount that everything is how I like it - save for one UDP port that was open. And yet, according to lsof, nothing. The strange part is that each time I scan, it's always random, on a different port. (note: no nameserver running)
    # nmap -p 0-65535 -sS -sU localhost

    Starting Nmap 4.11 ( Nmap - Free Security Scanner For Network Exploration & Security Audits. ) at 2010-02-13 18:36 EST
    Interesting ports on localhost.localdomain (127.0.0.1):
    Not shown: 131065 closed ports
    PORT STATE SERVICE
    25/tcp open smtp
    80/tcp open http
    443/tcp open https
    993/tcp open imaps
    57526/udp open unknown

    Nmap finished: 1 IP address (1 host up) scanned in 8.162 seconds
    # nmap -p 0-65535 -sS -sU localhost

    Starting Nmap 4.11 ( Nmap - Free Security Scanner For Network Exploration & Security Audits. ) at 2010-02-13 18:37 EST
    Interesting ports on localhost.localdomain (127.0.0.1):
    Not shown: 131065 closed ports
    PORT STATE SERVICE
    25/tcp open smtp
    80/tcp open http
    443/tcp open https
    993/tcp open imaps
    40756/udp open unknown

    Nmap finished: 1 IP address (1 host up) scanned in 8.418 seconds
    What do you think this could be from?
    A class that doesn't overload all operators just isn't finished yet. -- SmugCeePlusPlusWeenie
    A year spent in artificial intelligence is enough to make one believe in God. -- Alan J. Perlis

  2. #2
    spurious conceit MK27's Avatar
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    I think this it the famous whack-a-mole UDP port problem.



    Last edited by MK27; 02-13-2010 at 06:26 PM.
    C programming resources:
    GNU C Function and Macro Index -- glibc reference manual
    The C Book -- nice online learner guide
    Current ISO draft standard
    CCAN -- new CPAN like open source library repository
    3 (different) GNU debugger tutorials: #1 -- #2 -- #3
    cpwiki -- our wiki on sourceforge

  3. #3
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    'netstat -aup' should show you which process that owns the port

  4. #4
    Unregistered User Yarin's Avatar
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    No luck, 'netstat -aup' doesn't reveal anything lsof didn't.
    A class that doesn't overload all operators just isn't finished yet. -- SmugCeePlusPlusWeenie
    A year spent in artificial intelligence is enough to make one believe in God. -- Alan J. Perlis

  5. #5
    Registered User kryptkat's Avatar
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    it is netstat -aop

  6. #6
    Unregistered User Yarin's Avatar
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    No, Mike is right. -u checks for UDP sockets, -o displays timers. Why would I care about timers if I can't even see the socket?
    A class that doesn't overload all operators just isn't finished yet. -- SmugCeePlusPlusWeenie
    A year spent in artificial intelligence is enough to make one believe in God. -- Alan J. Perlis

  7. #7
    l'Anziano DavidP's Avatar
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    Maybe we should employ a numerologist to see if there is anything special about those port numbers?
    My Website

    "Circular logic is good because it is."

  8. #8
    Registered User kryptkat's Avatar
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    Displays protocol statistics and current TCP/IP network connections.

    NETSTAT [-a] [-e] [-n] [-o] [-s] [-p proto] [-r] [interval]

    -a Displays all connections and listening ports.
    -e Displays Ethernet statistics. This may be combined with the -s
    option.
    -n Displays addresses and port numbers in numerical form.
    -o Displays the owning process ID associated with each connection.
    -p proto Shows connections for the protocol specified by proto; proto
    may be any of: TCP, UDP, TCPv6, or UDPv6. If used with the -s
    option to display per-protocol statistics, proto may be any of:
    IP, IPv6, ICMP, ICMPv6, TCP, TCPv6, UDP, or UDPv6.
    -r Displays the routing table.
    -s Displays per-protocol statistics. By default, statistics are
    shown for IP, IPv6, ICMP, ICMPv6, TCP, TCPv6, UDP, and UDPv6;
    the -p option may be used to specify a subset of the default.
    interval Redisplays selected statistics, pausing interval seconds
    between each display. Press CTRL+C to stop redisplaying
    statistics. If omitted, netstat will print the current
    configuration information once.
    mine no have -u opps.

    i have theory if you like hear. your isp may use those udp ports to slip their advertisements on to your computer.meow i set up a listener on some udp ports to see why they were open. i did get a connect with the isp sending advertisements. fwiw

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