W32.Dumaru.Y@mm

SUMMARY

W32.Dumaru.Y@mm is a multi-threaded, mass-mailing worm that opens a backdoor, runs a keylogger, and attempts to steal personal information. It is similar to the W32.Dumaru.M@mm worm

This worm uses its own SMTP engine to spread to the email addresses it finds in the files on the infected system.

The email has the following characteristics:

From: "Elene" <F**KENSUICIDE@HOTMAIL.COM>  (censored)
Subject: Important information for you. Read it immediately !
Message:
Hi !
Here is my photo, that you asked for yesterday.
Attachment: Myphoto.zip

The attachment is a zip file that contains the worm executable as Myphoto.jpg   <spaces>  .exe. (There are 56 spaces between ".jpg" and ".exe".)

This worm is packed with FSG.

Protection

• Virus Definitions (LiveUpdate™ Weekly) January 26, 2004
• Virus Definitions (Intelligent Updater) January 26, 2004

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: Moderate

Damage

• Damage Level: Medium
• Payload: Sends itself to all the addresses it finds in the files with specific extensions.
• Releases Confidential Info: Logs keystrokes, emails personal information.
• Compromises Security Settings: Allows unauthorized remote access.

Distribution

• Distribution Level: High
• Subject of Email: Important information for you. Read it immediately !
• Name of Attachment: Myphoto.zip
• Size of Attachment: 17,613 bytes
• Ports: TCP ports 2283 and 10000

TECHNICAL DETAILS

When W32.Dumaru.Y@mm is executed, it does the following:

1. Copies itself as these files:
   • %System%l32x.exe
   • %System%vxd32v.exe
   • %Startup%dllxw.exe
     
     
     NOTES:
     • %System% is a variable: The worm locates the System folder and copies itself to that location. By default, this is C:WindowsSystem (Windows 95/98/Me), C:WinntSystem32 (Windows NT/2000), or C:WindowsSystem32 (Windows XP).
     • %Startup% is a variable: The worm locates the Windows startup folder and copies itself to that location. For example, this is C:WindowsStart MenuProgramsStartup in the Windows 98 system.
       
       
2. Adds the value:
   
   "load32"="%System%l32x.exe"
   
   to the registry key:
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRun
   
   so that the worm runs when you start Windows.
   
   
3. May create the registry key:
   
   HKEY_LOCAL_MACHINESOFTWARESARS
   
   
4. Modifies the [boot] section of the system.ini file (Windows 95/98/Me only) as follows:
   
   [boot]
   shell=explorer.exe %System%vxd32v.exe
   
   so that the worm runs when you start Windows 95/98/Me.
   
   
5. Modifies the Value data of: Shell
   
   in the registry key:
   
   HKEY_LOCAL_MACHINESoftwareMicrosoftWindows NTCurrentVersionWinlogon
   
   from:
   
   "explorer.exe"
   
   to:
   
   "explorer.exe %Windir%system32vxd32v.exe"
   
   so that the worm runs when you start Windows NT/2000/XP.
   
   
6. Retrieves email addresses from the files with the following extensions:
   • .htm
   • .wab
   • .html
   • .dbx
   • .tbb
   • .abd
     
     The email addresses will be saved in the file, %Windir%winload.log.
     
     
7. Creates the file, %Windir%Tempip.tmp, which contains the worm. Then, it uses its own SMTP engine to email the .zip file to the addresses it previously found.
   
   The email has the following characteristics:
   
   From: "Elene" <F**KENSUICIDE@HOTMAIL.COM> (censored)
   Subject: Important information for you. Read it immediately !
   Message:
   Hi !
   Here is my photo, that you asked for yesterday.
   Attachment: My photo.zip
   
   
8. Launches multiple new threads, and each thread is designed for a specific purpose. The threads will do the following:
   

• The first thread creates a WindowsHook, so that the worm gains control when certain actions occur on the system. This thread is designed to steal passwords, and it will log passwords as they are typed into Web forms and programs. They will be saved in the file, Vxdload.log.
  
  The worm may harvest passwords for a variety of programs; however, it specifically targets those for www.e-gold.com/. For any Web form on this site, the worm will begin logging all the keystrokes, which seems to be an attempt by the author of this worm to steal e-gold accounts.
  
  
• Another thread, which this worm launches, is responsible for copying certain information from the clipboard into the file, Rundllx.sys.
  
  
• If the worm does not find an Internet connection, only the first two threads are created. Then, the worm will go into an infinite loop, checking for an active Internet connection every 0.5 seconds. If it does find an active Internet connection, it will launch several more threads.
  
  
• The next two threads that this worm launches will open ports on the system and wait for incoming connections. One thread will listen on TCP port 10000, and the other one on TCP port 2283.
  
  
• The worm will periodically check the size of the files it uses for logging stolen information, and when sufficient in size, the log files will be emailed to a hard-coded email address.
  
  
• As this worm runs two backdoor threads, an attacker could access the system and gain full control, as well as use an infected computer as a relay.

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 malicious process.
4. Run a full system scan and delete all the files detected as W32.Dumaru.Y@mm.
5. Reverse the changes made to the registry.
6. Edit the System.ini file (Windows 95/98/Me).
   

For 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"

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Note: When you are completely finished with the removal procedure and you are satisfied that the threat has been removed, re-enable System Restore by following the instructions in the aforementioned documents.

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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 malicious process

Windows 95/98/Me
Shut down the computer and turn off the power. Wait for at least 30 seconds, and then restart the computer in Safe mode. For instructions, read the document, "How to start the computer in Safe Mode."

Windows NT/2000/XP
To end the malicious 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 "vxd32v.exe," "l32x.exe," or "dllxw.exe."
6. If you find one of these files, 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.Dumaru.Y@mm, click Delete.

5. Reversing the changes made to the registry

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WARNING: 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.

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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:
   
   "load32"="%System%l32x.exe""
   
   
5. Do one of the following:
   • If you are using Windows 95/98/Me, proceed to step i.
   • If you are using Windows NT/2000/Xp, proceed to step f.
     
     
6. Navigate to the key:
   
   HKEY_LOCAL_MACHINESoftwareMicrosoftWindows NTCurrentVersionWinlogon
   
   
7. In the right pane, double-click: Shell
   
   
8. Change:
   
   "explorer.exe %Windir%system32vxd32v.exe"
   
   to:
   
   "explorer.exe"
   
   
9. Exit the Registry Editor.
   
   
10. Restart the computer back into Normal mode. For instructions, read the section on returning to Normal mode in the document, "How to start the computer in Safe Mode."

6. Editing the System.ini file
If you are running Windows 95/98/Me, follow these steps:

1. The function you perform depends on your operating system:
   • Windows 95/98: Go to step b.
   • Windows Me: If you are running Windows Me, the Windows Me file-protection process may have made a backup copy of the System.ini file that you need to edit. If this backup copy exists, it will be in the C:WindowsRecent folder. Symantec recommends that you delete this file before continuing with the steps in this section. To do this:
     1. Start Windows Explorer.
     2. Browse to and select the C:WindowsRecent folder.
     3. In the right pane, select the System.ini file and delete it. The System.ini file will be regenerated when you save your changes to it in step F.
        
        
2. Click Start, and then click Run.
   
   
3. Type the following, and then click OK.
   
   edit c:windowssystem.ini
   
   (The MS-DOS Editor opens.)
   
   NOTE: If Windows is installed in a different location, make the appropriate path substitution.
   
   
4. In the [boot] section of the file, look for a line similar to:
   
   shell = Explorer.exe C:WINDOWSSYSTEMvxd32v.exe
   
   
5. If this line exists, delete everything to the right of Explorer.exe.
   
   When you are done, it should look like:
   
   shell = Explorer.exe
   
   
6. Click File, and then click Save.
   
   
7. Click File, and then click Exit.