W32.Sobig.D@mm

SUMMARY

W32.Sobig.D@mm is a mass-mailing worm that sends itself to all the email addresses it finds in the files with the following extensions:

• .wab
• .dbx
• .htm
• .html
• .eml
• .txt

The email falsely purports that admin@support.com sent it.

Email routine details
The email message has the following characteristics:

From: admin@support.com (NOTE: W32.Sobig.D@mm spoofs this field. It could be any address.)

Subject: The subject line will be one of the following:

• Re: Documents
• Re: App. 00347545-002
• Re: Movies
• Application Ref: 456003
• Re: Your Application (Ref: 003844)
• Re: Screensaver
• Re: Accepted
• Your Application

Message Body: See the attached file for details

Attachment: The attachment name will be one of the following:

• Document.pif
• app003475.pif
• movies.pif
• ref_456.pif
• Application844.pif
• Screensaver.scr
• Accepted.pif
• Applications.pif
• Application.pif

NOTE: The worm de-activates on July 2, 2003, and therefore, the last day on which the worm spreads is July 1, 2003.

Protection

• Virus Definitions (LiveUpdate™ Weekly) June 18, 2003
• Virus Definitions (Intelligent Updater) June 18, 2003

Threat Assessment

Wild

• Wild Level: Low
• Number of Infections: 0 - 49
• Number of Sites: 0 - 2
• Geographical Distribution: Low
• Threat Containment: Easy
• Removal: Easy

Damage

• Damage Level: Low

Distribution

• Distribution Level: High

TECHNICAL DETAILS

When W32.Sobig.D@mm is executed, it performs the following actions:

1. Copies itself as %Windir%cftrb32.exe.
   
   NOTE: %Windir% is a variable. The worm locates the Windows installation folder (by default, this is C:Windows or C:Winnt) and copies itself to that location.
   
   
2. Creates the following files, which it uses to store internal configuration data:
   • %Windir%dftrn32.dat
   • %Windir%ssp32.dat
     
     
3. Adds the value:
   
   "SFtrb Service"="%Windir%cftrb32.exe"
   
   to the registry key:
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRun
   
   so that W32.Sobig.D@mm runs when you start Windows.
   
   
4. If the operating system is Windows NT/2000/XP, then the worm will also add the value:
   
   "SFtrb Service"="%Windir%cftrb32.exe"
   
   to the registry key:
   
   HKEY_CURRENT_USERSOFTWAREMicrosoftWindowsCurrentVersionRun
   
   
5. Counts the Network Resources and copies itself to the following folders:
   • WindowsAll UsersStart MenuProgramsStartUp
   • Documents and SettingsAll UsersStart MenuProgramsStartup
     
     
6. Attempts to download data from particular Web pages.

W32.Sobig.D@mm is also network-aware. It counts the network resources and copies itself to the following folders on other computers to which it has access:

• WindowsAll UsersStart MenuProgramsStartUp
• Documents and SettingsAll UsersStart MenuProgramsStartup

Recommendations

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

• Turn off and remove unneeded services. By default, many operating systems install auxiliary services that are not critical, such as an FTP server, telnet, and a Web server. These services are avenues of attack. If they are removed, blended threats have less avenues of attack and you have fewer services to maintain through patch updates.
• If a blended 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 (for example, all Windows-based computers should have the current Service Pack installed.). Additionally, please apply any security updates that are mentioned in this writeup, in trusted Security Bulletins, or on vendor Web sites.
• 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.
• Configure your email server to block or remove email that contains file attachments that are commonly used to spread viruses, such as .vbs, .bat, .exe, .pif and .scr files.
• Isolate infected computers quickly to prevent further compromising your organization. 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.

REMOVAL

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. Do one of the following:
   • Windows 95/98/Me: Restart the computer in Safe mode.
   • Windows NT/2000/XP: End the Trojan process.
4. Run a full system scan and delete all the files detected as W32.Sobig.D@mm.
5. Find and delete the worms configuration files using the Windows Find or Search utility.
6. Delete the values that were added to the registry.

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

1. Disabling 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:

• "How to disable or enable Windows Me System Restore"
• "How to turn off or turn on Windows XP System Restore"

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. 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.

3. Restarting the computer in Safe mode or ending the Trojan process

Windows 95/98/Me
Restart the computer in Safe mode. All the Windows 32-bit operating systems, except for Windows NT, can be restarted in Safe mode. For instructions, read the document, "How to start the computer in Safe Mode."

Windows NT/2000/XP
To end the Trojan 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 Cftrb32.exe.
6. If you find the file, click it, and then click End Process.
7. Exit the Task Manager.

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.
   • For Norton AntiVirus consumer products: Read the document, "How to configure Norton AntiVirus to scan all files."
   • For Symantec AntiVirus Enterprise products: Read the document, "How to verify that a Symantec Corporate antivirus product is set to scan all files."
2. Run a full system scan.
3. If any files are detected as infected with W32.Sobig.D@mm, click Delete.

5. Finding and deleting files using the Windows Find or Search utility

Follow the instructions for your operating system:

• Windows 95/98/Me/NT/2000
  1. Click Start, point to Find or Search, and then click Files or Folders.
  2. Make sure that "Look in" is set to (C:) and that "Include subfolders" is checked.
  3. In the "Named" or "Search for..." box, type, or copy and paste, the file names:
     
     dftrn32.dat rssp32.dat
     
     
  4. Click Find Now or Search Now.
  5. Delete the displayed files.
  
  
• Windows XP
  1. Click Start, and then click Search.
  2. Click All files and folders.
  3. In the "All or part of the file name" box, type, or copy and paste, the file names:
     
     dftrn32.dat rssp32.dat
     
     
  4. Verify that "Look in" is set to "Local Hard Drives" or to (C:).
  5. Click "More advanced options."
  6. Check "Search system folders."
  7. Check "Search subfolders."
  8. Click Search.
  9. Delete the displayed files.
     
     

6. Deleting the values added to the registry

CAUTION: 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, and then click Run. (The Run dialog box appears.)
2. Type regedit
   
   Then click OK. (The Registry Editor opens.)
   
   
3. Navigate to the key:
   
   HKEY_LOCAL_MACHINESoftwareMicrosoftWindowsCurrentVersionRun
   
   
4. In the right pane, delete the value:
   
   "SFtrb Service"="%Windir%cftrb32.exe"
   
   
5. If the operating system is Windows NT/2000/XP, navigate to the key:
   
   HKEY_CURRENT_USERSOFTWAREMicrosoftWindowsCurrentVersionRun
   
   
6. In the right pane, delete the value:
   
   "SFtrb Service"="%Windir%cftrb32.exe"
   
   
7. Exit the Registry Editor.