W32.Sobig.B@mm

SUMMARY

NOTE: Due to a decreased rate of submissions, Symantec Security Response has downgraded this threat from Category 3 to Category 2 as of June 13, 2003.

W32.Sobig.B@mm is a mass-mailing worm that sends itself to all the email addresses, purporting to have been sent by Microsoft (support@microsoft.com). The worm finds the addresses in the files with the following extensions:

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

Email Routine Details
The email message has the following characteristics:

From: support@microsoft.com

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

• Your details
• Approved (Ref: 38446-263)
• Re: Approved (Ref: 3394-65467)
• Your password
• Re: My details
• Screensaver
• Cool screensaver
• Re: Movie
• Re: My application
  

Message Body: All information is in the attached file.

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

• your_details.pif
• ref-394755.pif
• approved.pif
• password.pif
• doc_details.pif
• screen_temp.pif
• screen_doc.pif
• movie28.pif
• application.pif

NOTES:

• The worm de-activates on May 31, 2003, and therefore, the last day on which the worm will spread is May 30, 2003.
• Virus definitions dated prior to May 19, 2003 may detect this threat as W32.HLLW.Mankx@mm.

Protection

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

Threat Assessment

Wild

• Wild Level: Medium
• Number of Infections: More than 1000
• Number of Sites: More than 10
• Geographical Distribution: Medium
• Threat Containment: Easy
• Removal: Easy

Damage

• Damage Level: Low
• Payload Trigger: Only activates on dates prior to 5/31/2003
• Large Scale E-mailing: Sends itself to e-mail addresses found on an infected machine

Distribution

• Distribution Level: High
• Subject of Email: Various
• Name of Attachment: various, all with a .pif extension
• Size of Attachment: 52,898 bytes
• Shared Drives: Attempts to copy itself to all the shared resources

TECHNICAL DETAILS

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

1. Copies itself as %Windir%msccn32.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:
   • %Windir%hnks.ini
   • %Windir%msdbrr.ini
     
     
3. Adds the value:
   
   "System Tray"="%Windir%msccn32.exe"
   
   to the registry key:
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRun
   
   so that W32.Sobig.B@mm runs when you start Windows.
   
   
4. If the operating system is Windows NT/2000/XP, then the worm will also add the value:
   
   "System Tray"="%Windir%msccn32.exe"
   
   to the registry key:
   
   HKEY_CURRENT_USERSOFTWAREMicrosoftWindowsCurrentVersionRun
   
   
5. Counts out the Network Resources and copies itself to the following folders:
   • WindowsAll UsersStart MenuProgramsStartUp
   • Documents and SettingsAll UsersStart MenuProgramsStartup
     
     
6. Attempts to download data from four different GeoCities Web pages. The addresses of these Web pages are stored in the aforementioned .ini files.
   

W32.Sobig.B@mm is also network-aware. It counts out 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

Removal using the W32.Sobig.B Removal Tool
Symantec Security Response has created a tool to remove W32.Sobig.B@mm, which is the easiest way to remove this threat.

Manual Removal
As an alternative to using the removal tool, you can manually remove this threat.

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

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

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

1. 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.

2. 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 Msccn32.exe.
6. If you find the file, click it, and then click End Process.
7. Exit the Task Manager.

3. 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.B@mm, click Delete.

4. Finding and deleting files

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 filenames:
     
     hnks.ini msdbrr.ini
     
     
  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 filenames:
     
     hnks.ini msdbrr.ini
     
     
  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.
  
  

5. Deleting the values from 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:
   
   "System Tray"="%Windir%msccn32.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:
   
   "System Tray"="%Windir%msccn32.exe"
   
   
7. Exit the Registry Editor.