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Discovered: August 18, 2003
Updated: February 13, 2007 12:05:02 PM
Type: Worm
Systems Affected: Windows

W32.Dinkdink.Worm is a worm that exploits the DCOM RPC vulnerability (described in Microsoft Security Bulletin MS03-026 ) using TCP port 135. The worm targets only Windows 2000 and Windows XP machines. While Windows NT and Windows 2003 Server machines are vulnerable to the aforementioned exploit if it is not properly patched, the worm is not coded to replicate to those systems.

W32.Dinkdink.Worm uses a two-step procedure to spread itself, using a fixed server from which to download itself. As of this writing, this server does not appear to contain a copy of the worm, it does therefore appear that the worm will no longer spread.

NOTE: Virus definitions dated August 19, 2003 may detect this threat as W32.Blaster.D.

Antivirus Protection Dates

  • Initial Rapid Release version August 19, 2003
  • Latest Rapid Release version September 28, 2010 revision 054
  • Initial Daily Certified version August 19, 2003
  • Latest Daily Certified version September 28, 2010 revision 036
  • Initial Weekly Certified release date August 19, 2003

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

Writeup By: Atli Gudmundsson

Discovered: August 18, 2003
Updated: February 13, 2007 12:05:02 PM
Type: Worm
Systems Affected: Windows

Once W32.Dinkdink.Worm is activated, it enters an infinite loop where it does the following:

  1. Generates a random class C address (A.B.C.x), where A equals one of the following:

    4 - 10% chance
    24 - 30% chance
    60 - 10% chance
    65 - 10% chance
    66 - 10% chance
    67 - 10% chance
    68 - 20% chance

  2. Iterates through A.B.C.0 - A.B.C.255, trying to connect to that IP on port 135.

  3. If a successful connection is established, the worm sends a data package that will try to exploit the DCOM RPC vulnerability.

    • While W32.Dinkdink.Worm cannot spread to the Windows NT or Windows Server 2003, unpatched computers running these operating systems may crash as a result of the worm's attempts to exploit them. However, if the worm is manually placed and executed on a computer running these operating systems, it can run and spread.
    • Due to the random nature of how the worm constructs the exploit data, this may cause the RPC service to crash if it receives incorrect data. This may manifest as svchost.exe, generating errors as a result of the incorrect data.
    • If the RPC service crashes, the default procedure under Windows XP and Windows Server 2003 is to restart the computer. To disable this feature, refer to step one of the "Removal Instructions" below.

  4. If the remote computer is vulnerable, the worm will direct it to download the file, Windat.exe, to %Sysdrive%\Documents and Settings\All Users\Start Menu\Programs\Startup on the vulnerable system, where it is subsequently executed.

    The worm accomplishes this by directing the Trivial File Transfer Protocol (TFTP) on the vulnerable computer to download Windat.exe from a third computer, whose name is hard-coded in the worm.

    NOTES: As of this writing, this remote computer appears to be down.


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: Atli Gudmundsson

Discovered: August 18, 2003
Updated: February 13, 2007 12:05:02 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. Restore Internet connectivity.
  2. End the worm process.
  3. Obtain the latest virus definitions.
  4. Scan for and delete the infected files.
  5. Obtain the Microsoft HotFix to correct the DCOM RPC vulnerability

For specific details on each of these steps, read the following instructions.

1. Restoring Internet connectivity
In many cases, on both Windows 2000 and XP, changing the settings for the Remote Procedure Call (RPC) service may allow you to connect to the Internet without the computer shutting down. To restore Internet connectivity to your PC, follow these steps:
    1. Click Start > Run. The Run dialog box appears.
    2. Type:


      in the open line, and then click OK. The Services window opens.

    3. In the left pane, double-click Services and Applications, and then select Services. A list of services appears.
    4. In the right pane, locate the Remote Procedure Call (RPC) service.

      CAUTION: There is also a service named Remote Procedure Call (RPC) Locator. Do not confuse the two.

    5. Right-click the Remote Procedure Call (RPC) service, and then click Properties.
    6. Click the Recovery tab.
    7. Using the drop-down lists, change First failure, Second failure, and Subsequent failures to "Restart the Service."
    8. Click Apply, and then OK.

      CAUTION: Make sure that you change these settings back once you have removed the worm.

2. Ending the Worm process
  1. Press Ctrl+Alt+Delete once.
  2. Click Task Manager.
  3. Click the Processes tab.
  4. Double-click the Image Name column header to alphabetically sort the processes.
  5. Scroll through the list and look for windat.exe and nvnet.exe
  6. If you find either file, click it, and then click End Process.
  7. Exit the Task Manager.

3. Updating 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.

4. Scanning for and deleting 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.Dinkdink.Worm, click Delete.

5. Obtaining the Microsoft HotFix to correct the DCOM RPC vulnerability
W32.Blaster.Worm is a worm that exploits the DCOM RPC vulnerability using TCP port 135 to infect your PC. The W32.Blaster.Worm also attempts to perform a DoS on the Microsoft Windows Update Web server (windowsupdate.com) using your PC. To fix this, it is important to obtain the Microsoft Hotfix at: Microsoft Security Bulletin MS03-026 .

Writeup By: Atli Gudmundsson