Discovered: November 11, 2004
Updated: February 13, 2007 12:29:50 PM
Type: Worm
Systems Affected: Windows

W32.Scard is a worm with backdoor functionality that uses a NetBIOS attack to spread to systems that have weak passwords.

Antivirus Protection Dates

  • Initial Rapid Release version November 11, 2004
  • Latest Rapid Release version August 08, 2016 revision 023
  • Initial Daily Certified version November 11, 2004
  • Latest Daily Certified version August 09, 2016 revision 001
  • Initial Weekly Certified release date November 17, 2004

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

Writeup By: Rodney Andres

Discovered: November 11, 2004
Updated: February 13, 2007 12:29:50 PM
Type: Worm
Systems Affected: Windows

When W32.Scard runs, it performs the following actions:

  1. Creates the following files:
    • %System%\Alerter.exe
    • %System%\spc.exe
    • %System%\comwsock.dll
    • %System%\dmsock.dll
    • %System%\SCardSer.exe
    • %System%\sptres.dll

      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).

  2. Injects the file sptres.dll into the Explorer.exe process.

  3. Scans for computers with weak passwords and attempt to perform a NetBIOS attack on them.

  4. Attempts to copy itself to a remote computer as one of the following, using a list of predetermined passwords:

    • ADMIN$\System32\Alerter.exe
    • ADMIN$\System32\Alerter16.exe

      The passwords the worm uses for the NetBIOS attack are the following:

    • stgzs
    • security
    • super
    • oracle
    • secret
    • root
    • admin
    • password
    • passwd
    • pass
    • 88888888
    • 888888
    • 00000000
    • 000000
    • 11111111
    • 111111
    • 111
    • fan@ing*
    • 54321
    • 654321
    • ~!@#
    • !@#$%^
    • !@#$%
    • !@#$
    • 12345!@#$%
    • 1234!@#$
    • 123!@#
    • 12345678
    • 1234567
    • 123456
    • 12345
    • 1234
    • 123

  5. Creates the following registry entries:


    so that the service "netlog" is created, and the worm is executed every time Windows starts.

    The service "netlog" has the following characteristics:
    Display name: "Net Login Helper"
    References: %System%\SCardSer.exe

  6. Injects the file comwsock.dll into the Lsass.exe process.

    The file comwsock.dll, in turn, attempts to inject the file dmsock.dll into the following processes:
    • svchost.exe
    • explorer.exe
    • inetinfo.exe
    • qq.exe
    • msimn.exe
    • iexplore.exe
    • outlook.exe
    • msmsgs.exe
    • msnmsgr.exe

  7. Opens a backdoor that is opened on a random port while running in the process space of the above processes.

  8. W32.Scard can also be installed by exploiting Mircrosoft Windows WMF/EMF Image Format Rendering Remote Buffer Overflow Vulnerability, which is described in MS04-032. This exploit code spreads as an EMF file attached to email message.
    If a user opens the message, it creates W32.Scard as the following file name and executes it:
    • %system%\spo0lsv.exe


    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: Rodney Andres

    Discovered: November 11, 2004
    Updated: February 13, 2007 12:29:50 PM
    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.Scard.
    5. Reverse the changes made to the registry.
    For details on each of these steps, read the following instructions.

    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:

    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 daily. 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.Scard, click Delete.

    5. To reverse the changes made to the registry

    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.
    2. Type regedit

      Then click OK.

    3. Navigate to and delete the following keys:


    4. Exit the Registry Editor.

    5. 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: Rodney Andres