Discovered: January 18, 2002
Updated: February 13, 2007 11:57:39 AM
Also Known As: W32.Suns
Type: Virus


W32.Sinus is an antiheuristic virus that infects programs in shared directories and programs when it is executed from Windows Explorer. The virus opens a backdoor to the infected Windows 95/98/Me-based computer.

Antivirus Protection Dates

  • Initial Rapid Release version January 21, 2002
  • Latest Rapid Release version September 28, 2010 revision 054
  • Initial Daily Certified version January 21, 2002
  • Latest Daily Certified version September 28, 2010 revision 036

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

Writeup By: Frederic Perriot

Discovered: January 18, 2002
Updated: February 13, 2007 11:57:39 AM
Also Known As: W32.Suns
Type: Virus


When W32.Sinus is executed, there is a 1-in-8 chance that it will infect all .exe programs in all shared directories on the computer.

The virus determines which version of Windows is installed on the computer. If the computer is running Windows 95, 98, or Me, then the virus creates a new full-access share for the Windows directory. It then disables the remote administration dialog in the Passwords Control Panel applet. The share is named ADMIN$ and is protected by a password that is known to the virus author and hidden from the user of the computer by a registry trick.

Finally, the virus copies itself to the system directory and modifies the following registry key to point to the virus:

HKEY_CLASSES_ROOT\exefile\shell\open\command

This causes the virus to be executed and a program to be infected whenever an executable file is launched from Windows Explorer.

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: Frederic Perriot

Discovered: January 18, 2002
Updated: February 13, 2007 11:57:39 AM
Also Known As: W32.Suns
Type: Virus


To remove this virus, scan the computer using the latest virus definitions and delete any infected files. Then edit the registry to remove the entries that the virus created. Follow these steps in the order listed.

To remove the virus:

  1. Run LiveUpdate to make sure that you have the most recent virus definitions.
  2. Start Norton AntiVirus (NAV), and make sure that NAV is configured to scan all files. For instructions on how to do this, read the document How to configure Norton AntiVirus to scan all files.
  3. Run a full system scan.
  4. Delete any files that are detected as infected by W32.Sinus. Replace deleted files from a clean backup or reinstall them.

To edit the registry:

CAUTION : We strongly recommend that you back up the registry before you make any changes to it. Incorrect changes to the registry can result in permanent data loss or corrupted files. Modify only the keys that are specified. Read the document How to back up the Windows registry for instructions.
  1. Click Start, and click Run. The Run dialog box appears.
  2. Type regedit and then click OK. The Registry Editor opens.
  3. Open the following key:

    HKEY_CLASSES_ROOT\exefile\shell\open\command

    IMPORTANT CAUTION: The \Classes subkey contains many subkey entries that refer to other file extensions. One of these file extensions is .exe. Changing this extension can prevent any files ending with an .exe extension from running. Make sure you browse all the way along this path until you reach the \command subkey.

    Do not
    modify the HKEY_CLASSES_ROOT\Software\Classes\.exe key.
    Do modify the HKEY_CLASSES_ROOT\Software\Classes\exefile\shell\open\command subkey that is shown in the following figure.

    <<=== NOTE: This is the key that you need to modify.

  4. Double-click the (Default) value in the right pane.
  5. Delete the current value data. Make sure that you completely delete all value data in the \command key before you continue to the next step. If you leave a space at the beginning of the entry, any attempt to run program files will result in the error message, "Windows cannot find .exe." If this happens to you, start over at the beginning of this document, making sure to completely remove the current value data.
  6. Type "%1" %* (quote-percent-one-quote-space-percent-asterisk).

    NOTE: The Registry Editor will automatically enclose the value within quotation marks. After you click OK, the (Default) value should look exactly like this:

    ""%1" %*"
  7. Open the following key:

    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Network\LanMan
  8. In the right pane, delete the following value:

    ADMIN$
  9. Click Registry, and click Exit.
  10. Restart the computer.


Writeup By: Frederic Perriot