Worm:W32/Zotob.A is a clone of Worm:W32/Mytob.A that spreads using a vulnerability in Windows Plug and Play service (MS05-039).

Automatic action

Based on the settings of your F-Secure security product, it will either move the file to the quarantine where it cannot spread or cause harm, or remove it.

Suspect a file is incorrectly detected (a False Positive)?

A False Positive is when a file is incorrectly detected as harmful, usually because its code or behavior resembles known harmful programs. A False Positive will usually be fixed in a subsequent database update without any action needed on your part. If you wish, you may also:

  • Check for the latest database updates

    First check if your F-Secure security program is using the latest detection database updates, then try scanning the file again.

  • Submit a sample

    After checking, if you still believe the file is incorrectly detected, you can submit a sample of it for re-analysis.

    NOTE If the file was moved to quarantine, you need to collect the file from quarantine before you can submit it.

  • Exclude a file from further scanning

    If you are certain that the file is safe and want to continue using it, you can exclude it from further scanning by the F-Secure security product.

    Note You need administrative rights to change the settings.

For more Support


Find the latest advice in our Community.

User Guide

See the user guide for your product on the Help Center.

Contact Support

Chat with or call an expert for help.

Submit a sample

Submit a file or URL for further analysis.

Technical Details

The worm is a packed PE executable file 22528 bytes long.


When run, the worm saves a copy of itself to the System directory using the name "botzor.exe" and creates a mutex named "B-O-T-Z-O-R" to ensure only one copy of the worm is run at any one time.

It then adds the following registry entries to ensure that it is started when a user logs on or the system is restarted:

  • [HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run]
  • [HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\RunServices] "WINDOWS SYSTEM" = "botzor.exe"

The worm also adds the following registry key to diasable shared access service:

  • [HKLM\SYSTEM\CurrentControlSet\Services\SharedAccess] "Start" = "4"


To propagate itself, the worm scans for systems vulnerable to Microsoft Windows Plug and Play service (MS05-039) through TCP/445. The exploit uses fixed offsets inside Windows 2000 version of umpnpmgr.dll. This means that only Windows 2000 systems (SP0-4) are affected. Please see the following page for detailed information on the vulnerability: http://www.microsoft.com/technet/security/Bulletin/MS05-039.mspx

To scan for vulnerable systems, Zotob creates 300 threads that connect to random IP addresses within the B-class ( network of the infected system. It first tests connection to port 445 and if successful, it tries to exploit the vulnerability.

If the attack is successful, a command shell is started on the remote computer's port 8888. Through the shell port, the worm sends a FTP script which instructs the remote computer to download and execute the worm from the attacker computer using FTP.

All infected computers listen on port 33333 in order to serve out the worm to other hosts being infected. The downloaded file is saved as 'haha.exe' on disk.

Here is the summary of the ports used in attack:

  • Port 445 - The worm scans for systems vulnerable to PnP exploit through this port
  • Port 33333 - FTP server port on infected systems
  • Port 8888 - The command shell port opened by the exploit code

Bot functionality

The worm tries to connect to a predefined IRC channel. An attacker who knows channel password can instruct the bot to execute the following actions:

  • Disconnect/reconnect from the IRC channel.
  • Request system information.
  • Download and execute files.
  • Remove worm from the system
  • Manipulate the system security settings.


Zotob.A modifies the system hosts file to disable access to certain sites. The following hostnames are redirected to localhost IP address (

  • avp.com
  • ca.com
  • customer.symantec.com
  • dispatch.mcafee.com
  • download.mcafee.com
  • ebay.com
  • f-secure.com
  • kaspersky.com
  • kaspersky-labs.com
  • liveupdate.symantec.com
  • liveupdate.symantecliveupdate.com
  • mast.mcafee.com
  • mcafee.com
  • microsoft.com
  • moneybookers.com
  • my-etrust.com
  • nai.com
  • networkassociates.com
  • pandasoftware.com
  • paypal.com
  • rads.mcafee.com
  • secure.nai.com
  • securityresponse.symantec.com
  • sophos.com
  • symantec.com
  • trendmicro.com
  • updates.symantec.com
  • update.symantec.com
  • us.mcafee.com
  • viruslist.com
  • virustotal.com
  • www.amazon.com
  • www.avp.com
  • www.ca.com
  • www.ebay.com
  • www.f-secure.com
  • www.grisoft.com
  • www.kaspersky.com
  • www.mcafee.com
  • www.microsoft.com
  • www.moneybookers.com
  • www.my-etrust.com
  • www.nai.com
  • www.networkassociates.com
  • www.pandasoftware.com
  • www.paypal.com
  • www.sophos.com
  • www.symantec.com
  • www.trendmicro.com
  • www.virustotal.com

The worm also writes the following text to hosts file:

  • Botzor2005 Made By .... Greetz to good friend Coder. Based On HellBot3
  • MSG to avs: the first av who detect this worm will be the first killed in the next 24hours!!!