W32.Erkez.C@mm

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Discovered: October 27, 2004
Updated: February 13, 2007 12:29:11 PM
Also Known As: W32/Zafi.c@MM [McAfee], Zafi.C [F-Secure], W32/Zafi.C.worm [Panda], I-Worm.Zafi.c [Kaspersky], WORM_ZAFI.C [Trend Micro]
Type: Worm
Systems Affected: Windows


W32.Erkez.C@mm is a mass-mailing worm that sends itself to email addresses it finds on the infected computer. It also copies itself to folders that are likely to be shared on file-sharing networks.

When this worm infects a computer, it attempts to overwrite .exe files. The files that it targets are usually executables that belong to security products, including Symantec products. However, in some cases, the worm may overwrite .exe files that belong to other programs.

If the worm does overwrite .exe files, some programs or operating system functions may no longer function correctly.

Antivirus Protection Dates

  • Initial Rapid Release version October 28, 2004
  • Latest Rapid Release version September 28, 2010 revision 054
  • Initial Daily Certified version October 28, 2004
  • Latest Daily Certified version September 28, 2010 revision 036
  • Initial Weekly Certified release date October 29, 2004

Click here for a more detailed description of Rapid Release and Daily Certified virus definitions.

Writeup By: Yana Liu

Discovered: October 27, 2004
Updated: February 13, 2007 12:29:11 PM
Also Known As: W32/Zafi.c@MM [McAfee], Zafi.C [F-Secure], W32/Zafi.C.worm [Panda], I-Worm.Zafi.c [Kaspersky], WORM_ZAFI.C [Trend Micro]
Type: Worm
Systems Affected: Windows


When W32.Erkez.C@mm is executed, it performs the following actions:

  1. Creates a mutex "UpdateZ3", so that only one instance of the worm runs on the computer.

  2. Copies itself as the following:

    %System%\svchost.com
    %System%\svchost.con

    Note: %System% is a variable that refers to the System folder. By default this is C:\Windows\System (Windows 95/98/Me), C:\Winnt\System32 (Windows NT/2000), or C:\Windows\System32 (Windows XP).

  3. Creates some files in the %System% folder under the name svchost.co[random digit].

  4. Adds the value:

    "_svchost.con"="%System%\svchost.com"

    to the registry key:

    HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run

    so that the worm runs when you start Windows.

  5. Creates the registry key:

    HKEY_LOCAL_MACHINE\Software\Microsoft\UpdateZ3

    to store information about itself.

  6. Modifies the following registry key values:

    "DisableNotifications" = "1"
    "EnableFirewall" = "0"
    "DoNotAllowExceptions" = "0"

    in the key

    HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\SharedAccess\
    Parameters\FirewallPolicy\StandardProfile

    to disable anti-virus and security applications.

  7. Modifies the following registry key values:

    "AntiVirusDisableNotify" = "1"
    "FirewallDisableNotify" = "1"
    "UpdatesDisableNotify" = "1"
    "AntiVirusOverride" = "1"
    "FirewallOverride" = "1"

    in the key

    HKEY_LOCAL_MACHINE\Software\Microsoft\Security Center

    to disable anti-virus and security applications.

  8. Creates a log file c:\tm.txt.

  9. Prevents users from running applications whose name contain any of the following strings:
    • reged
    • msconfig
    • task

  10. Searches the computer for files or folders that belong to known anti-virus and security products, including Symantec products:
    • If the worm finds such a file, the worm will overwrite it with a copy of itself.
    • If the worm finds such a folder, the worm will overwrite all .exe files in that folder and in any subfolders with a copy of itself. As a result, the worm will overwrite .exe files in the following folders and in their subfolders:
      • C:\Program Files\Symantec
      • C:\Program Files\Norton AntiVirus

        Note: The worm is not limited to the above folders, and may overwrite files in other locations.
        Searches the computer for the files or folders that belong to known security products, including Symantec products:

  11. Searches for folders on drives C through H with names that contain the strings "share", "upload", and "downlo".

    The worm will copy itself to the folders that it finds as one of the following:
    • doom3 keygen.exe
    • the randomly chosen file name

      The worm also selects a file name at random from the infected computer that contains any of the following strings:
    • office
    • nero
    • icq
    • game
    • winra
    • winzi
    • divx
    • movie
    • total
    • wina
    • key
    • crack
    • serial
    • instal
    • full

      and copies itself to the folder found above using this file name.

  12. Searches for email addresses on the infected computer and stores them in the files %System%\svchost.co[random digit]. The worm retrieves email addresses from the Windows address book, and from files with the following extensions:
    • .htm
    • .wab
    • .txt
    • .dbx
    • .tbb
    • .asp
    • .php
    • .sht
    • .adb
    • .mbx
    • .eml
    • .pmr

      The worm does not copy email addresses that contain the following substrings:
    • info
    • help
    • aol
    • webm
    • micro
    • msn
    • hotmail
    • co
    • suppor
    • syma
    • vir
    • trend
    • panda
    • hoo
    • com
    • cafee
    • sopho
    • google
    • kasper

  13. Uses its own SMTP engine to send itself to the email addresses it gathered from the infected computer. The email message may be written in several different languages. It includes a copy of the worm as an attachment, which may have a double extension.

  14. Performs a Denial of Service (DoS) attack by sending numerous HTTP get requests to the www.miniszterelnok.hu domain.


Recommendations

Symantec Security Response encourages all users and administrators to adhere to the following basic security "best practices":

  • Use a firewall to block all incoming connections from the Internet to services that should not be publicly available. By default, you should deny all incoming connections and only allow services you explicitly want to offer to the outside world.
  • Enforce a password policy. Complex passwords make it difficult to crack password files on compromised computers. This helps to prevent or limit damage when a computer is compromised.
  • Ensure that programs and users of the computer use the lowest level of privileges necessary to complete a task. When prompted for a root or UAC password, ensure that the program asking for administration-level access is a legitimate application.
  • Disable AutoPlay to prevent the automatic launching of executable files on network and removable drives, and disconnect the drives when not required. If write access is not required, enable read-only mode if the option is available.
  • Turn off file sharing if not needed. If file sharing is required, use ACLs and password protection to limit access. Disable anonymous access to shared folders. Grant access only to user accounts with strong passwords to folders that must be shared.
  • Turn off and remove unnecessary services. By default, many operating systems install auxiliary services that are not critical. These services are avenues of attack. If they are removed, threats have less avenues of attack.
  • If a threat exploits one or more network services, disable, or block access to, those services until a patch is applied.
  • Always keep your patch levels up-to-date, especially on computers that host public services and are accessible through the firewall, such as HTTP, FTP, mail, and DNS services.
  • Configure your email server to block or remove email that contains file attachments that are commonly used to spread threats, such as .vbs, .bat, .exe, .pif and .scr files.
  • Isolate compromised computers quickly to prevent threats from spreading further. Perform a forensic analysis and restore the computers using trusted media.
  • Train employees not to open attachments unless they are expecting them. Also, do not execute software that is downloaded from the Internet unless it has been scanned for viruses. Simply visiting a compromised Web site can cause infection if certain browser vulnerabilities are not patched.
  • If Bluetooth is not required for mobile devices, it should be turned off. If you require its use, ensure that the device's visibility is set to "Hidden" so that it cannot be scanned by other Bluetooth devices. If device pairing must be used, ensure that all devices are set to "Unauthorized", requiring authorization for each connection request. Do not accept applications that are unsigned or sent from unknown sources.
  • For further information on the terms used in this document, please refer to the Security Response glossary.

Writeup By: Yana Liu

Discovered: October 27, 2004
Updated: February 13, 2007 12:29:11 PM
Also Known As: W32/Zafi.c@MM [McAfee], Zafi.C [F-Secure], W32/Zafi.C.worm [Panda], I-Worm.Zafi.c [Kaspersky], WORM_ZAFI.C [Trend Micro]
Type: Worm
Systems Affected: Windows


The following instructions pertain to all current and recent Symantec antivirus products, including the Symantec AntiVirus and Norton AntiVirus product lines.

  1. Disable System Restore (Windows Me/XP).
  2. Update the virus definitions.
  3. Restart the computer in Safe mode or VGA mode.
  4. Run a full system scan and delete all the files detected as W32.Erkez.C@mm.
  5. Reverse the changes made to the registry.
For specific details on each of these steps, read the following instructions.


Important: Alternate steps if the worm has already run.
If the worm has already run, it may have overwritten files that Symantec AntiVirus and Norton AntiVirus products require. If you cannot start your Norton or Symantec antivirus product in steps 2 or 4, follow this alternate procedure:
  1. Restart in Safe mode or VGA mode (step 3.).
  2. Edit the registry (step 5).
  3. Restart in Normal mode.
  4. Re-install Symantec AntiVirus or Norton AntiVirus.
  5. Follow steps 1 through 5.



1. To disable System Restore (Windows Me/XP)
If you are running Windows Me or Windows XP, we recommend that you temporarily turn off System Restore. Windows Me/XP uses this feature, which is enabled by default, to restore the files on your computer in case they become damaged. If a virus, worm, or Trojan infects a computer, System Restore may back up the virus, worm, or Trojan on the computer.

Windows prevents outside programs, including antivirus programs, from modifying System Restore. Therefore, antivirus programs or tools cannot remove threats in the System Restore folder. As a result, System Restore has the potential of restoring an infected file on your computer, even after you have cleaned the infected files from all the other locations.

Also, a virus scan may detect a threat in the System Restore folder even though you have removed the threat.

For instructions on how to turn off System Restore, read your Windows documentation, or one of the following articles:
Note: When you are completely finished with the removal procedure and are satisfied that the threat has been removed, re-enable System Restore by following the instructions in the aforementioned documents.

For additional information, and an alternative to disabling Windows Me System Restore, see the Microsoft Knowledge Base article, "Antivirus Tools Cannot Clean Infected Files in the _Restore Folder," Article ID: Q263455.

2. To update the virus definitions
Symantec Security Response fully tests all the virus definitions for quality assurance before they are posted to our servers. There are two ways to obtain the most recent virus definitions:

  • Running LiveUpdate, which is the easiest way to obtain virus definitions: These virus definitions are posted to the LiveUpdate servers once each week (usually on Wednesdays), unless there is a major virus outbreak. To determine whether definitions for this threat are available by LiveUpdate, refer to the Virus Definitions (LiveUpdate).
  • Downloading the definitions using the Intelligent Updater: The Intelligent Updater virus definitions are posted on U.S. business days (Monday through Friday). You should download the definitions from the Symantec Security Response Web site and manually install them. To determine whether definitions for this threat are available by the Intelligent Updater, refer to the Virus Definitions (Intelligent Updater).

    The Intelligent Updater virus definitions are available: Read "How to update virus definition files using the Intelligent Updater" for detailed instructions.

3. To restart the computer in Safe mode or VGA mode
Shut down the computer and turn off the power. Wait for at least 30 seconds, and then restart the computer in Safe mode or VGA mode.
  • For Windows 95, 98, Me, 2000, or XP users, restart the computer in Safe mode. For instructions, read the document, "How to start the computer in Safe Mode."
  • For Windows NT 4 users, restart the computer in VGA mode.


4. To scan for and delete the infected files
  1. Start your Symantec antivirus program and make sure that it is configured to scan all the files.
  2. Run a full system scan.
  3. If any files are detected as infected with W32.Erkez.C@mm, click Delete.

5. To reverse the changes made to the registry


WARNING: Symantec strongly recommends that you back up the registry before making any changes to it. Incorrect changes to the registry can result in permanent data loss or corrupted files. Modify the specified keys only. Read the document, "How to make a backup of the Windows registry ," for instructions.
  1. Click Start > Run. (The Run dialog box appears.)
  2. Type regedit

    Then click OK. (The Registry Editor opens.)

  3. Navigate to the key:

    HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run

  4. In the right pane, delete the value:

    "_svchost.con"="%System%\svchost.com"

  5. Navigate to the key and delete it:

    HKEY_LOCAL_MACHINE\Software\Microsoft\UpdateZ3

  6. Exit the Registry Editor.

  7. Restart the computer in Normal mode. For instructions, read the section on returning to Normal mode in the document, "How to start the computer in Safe Mode."


Writeup By: Yana Liu