W32.Navidad

W32.Navidad is a mass-mailing worm program. Using MAPI, the worm replies to all inbox messages that contain a single attachment. This worm is able to distribute itself through any MAPI-compliant email client, including Microsoft Outlook. However, email messages that are infected with this worm can be received by any email client. The worm utilizes the existing email subject line and body and attaches itself as Navidad.exe. Due to the bugs in the code, when the worm is executed, it causes your system to be unusable. Symantec has also created an interactive tutorial to help you get rid of this worm.

Also Known As:	I-Worm.Navidad.a [Kaspersky], W32/Navidad.gen@M [McAfee], Win32.Navidad [Computer Associates], W32/Navidad [Sophos], WORM_NAVIDAD.A [Trend]
Type:	Worm
Infection Length:	32,768 bytes
Systems Affected:	Windows 95, Windows 98, Windows NT, Windows 2000, Windows XP, Windows Me
Systems Not Affected:	Windows 3.x, Macintosh, UNIX, Linux

Virus Definitions (LiveUpdate™ Weekly) November 06, 2000 Virus Definitions (Intelligent Updater) November 06, 2000

Wild Number of infections: More than 1000 Number of sites: More than 10 Geographical distribution: High Threat containment: Moderate Removal: Difficult

Threat Metrics Wild: Low Damage: High Distribution: High

Damage

• Payload:
  • Large scale e-mailing: Uses MAPI commands to reply to all inbox messages that contain a single attachment.
  • Causes system instability: Improperly changes registry keys

Distribution

• Subject of email: Uses existing subject lines
• Name of attachment: NAVIDAD.EXE
• Size of attachment: 32,768 bytes

NOTE: If you are running Windows 95 or Windows 98, it is assumed that Windows is located in C:\Windows. If you are running Windows NT or Windows 2000, it is assumed that Windows is located in C:\Winnt. If Windows is installed in a different directory, make the appropriate substitutions.

This is how the worm works:

1. When executed, the worm displays a dialog box with the cryptic letters
   
   UI
   
   and the title
   
   Error
   
2. If you are running Windows 95 or Windows 98, the worm adds the following registry key:
   
   HKEY_USERS\.DEFAULT\Software\Navidad
   
   If you are running Windows NT or Windows 2000, the worm adds the following registry key:
   
   HKEY_CURRENT_USER\Software\Navidad
   
   This key was supposed to be used to see if the computer was already infected. However, due to bugs in the code, the registry key is not used.
   
3. If you are running Windows 95 or Windows 98, the worm adds the following registry key:
   
   HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
   
   with the value
   
   Win32BaseServiceMOD=\Windows\System\Winsvrc.exe
   
   If you are running Windows NT or Windows 2000, the worm adds the following registry key:
   
   HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
   
   with the value
   
   Win32BaseServiceMOD=\Winnt\System32\Winsvrc.exe
   
4. The worm copies itself into the Windows system folder as Winsvrc.vxd. Due to the difference in file name, the virus does not execute properly at startup. After the file has been copied, the worm modifies two additional registry keys. If you are running Windows 95 or Windows 98, the worm changes
   
   HKEY_LOCAL_MACHINE\SOFTWARE\CLASSES\exefile\shell\open\command
   HKEY_CLASSES_ROOT\exefile\shell\open\command
   
   to equal
   
   \Windows\System\winsvrc.exe "%1" %*"
   
   If you are running Windows NT or Windows 2000, the worm changes
   
   HKEY_LOCAL_MACHINE\SOFTWARE\CLASSES\exefile\shell\open\command
   HKEY_CLASSES_ROOT\exefile\shell\open\command
   
   to equal
   
   \Winnt\System32\winsvrc.exe "%1" %*"
   
   Due to the mistake in the file name, the system is unusable. Whenever an .exe file is executed, the Windows prompts you for the location of Winsvrc.exe. The net result is that no program files can be launched. This may cause system instability and you may have difficulty restarting the system.
   
5. Next, the worm begins the email routine. The worm uses MAPI to send mail and works with any MAPI-compliant email client, including Microsoft Outlook. The worm checks for all messages in your Inbox and replies to those messages that have one attachment. The reply consists of the same subject line and body, but contains the worm attached as NAVIDAD.EXE.
   
6. Finally, the worm places a blue eye icon in the system tray of the taskbar. When the mouse pointer is over the icon, the worm displays a yellow dialog box that states
   
   Lo estamos mirando... (In English: We are watching it...)
   
   When you click the icon, a dialog box with a button appears. The button contains the following text:
   
   Nunca presionar este boton (In English: Never press this button)
   
   If you click the button, an error box with the title
   
   Feliz Navidad (In English: Merry Christmas)
   
   displays the message
   
   Lamentablemente cayo en la tentacion y perdio su computadora (In English: Unfortunately you've fallen to temptation and have lost your computer)
   
   If you close the dialog box by clicking the X instead of clicking the button, the following message appears:
   
   buena eleccion (In English: Good selection)
   
   and exits. Despite the warning of losing the computer, no further changes are made to the system.

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.

The Symantec AntiVirus Research Center (SARC) has developed a tool to help you repair the damage done by the worm. The W32.Navidad Fix Tool, and instructions on how to use it, are available here.

If you prefer to remove the worm without using the tool, or if the tool does not work on your computer, then follow the instructions in each section in the order shown. We strongly recommend that you read and understand the entire procedure before proceeding.

To remove this worm, you must do the following:

• Copy Regedit.exe to Regedit.com (in some cases).
• Edit the registry, and remove keys and changes made by the worm.
• Set Windows to show all files.
• Delete files placed on the computer by the worm.
• Run a full system scan.

1. Do one of the following, depending on which operating system you have installed:
   • Windows 95/98. Click Start, point to Programs, and then click MS-DOS Prompt.
   • Windows Me. Click Start, point to Programs, point to Accessories, and then click MS-DOS Prompt.
   • Windows 2000.
     1. Click Start, and click Run.
     2. Click Browse, and then browse to the \Winnt\System32 folder.
     3. Double-click the Command.com file, and then click OK.
     4. Type cd \winnt and then press Enter.
2. Type copy regedit.exe regedit.com and then press Enter.
3. Type start regedit.com and then press Enter.
4. Proceed to the section "To edit the registry and remove keys and changes made by the worm."
   
   NOTE: This will open the Registry Editor in front of the DOS window. After you finish editing the registry and have closed the Registry Editor, close the DOS window as well.

1. Start the Registry Editor if necessary:
   • If you have performed the procedure in the previous section, the Registry Editor is already open. Skip to step 4.
   • If it was not necessary to perform the procedures in the previous section, go on to step 2.
2. Click Start, and click Run. The Run dialog box appears.
3. Type regedit and then click OK. The Registry Editor opens.
   
   NOTE: If you see an error message or the Registry Editor does not open, go back to and follow the instructions in the previous section.
   
4. Navigate to and delete the following keys:
   
   NOTE: It is likely that you will find only one.
   
   HKEY_CURRENT_USER\Software\Navidad
   HKEY_CURRENT_USER\Software\Emanuel
   
5. Navigate to and select the following key:
   
   HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run
   
6. In the right pane, look for and select any of the following values that exist:
   
   Win32BaseServiceMOD         C:\Windows\System\winsvrc.exe
   Win32BaseServiceMOD         C:\Windows\System\wintask.exe
   
   NOTE: Some other variants of this have been seen, such as win b service. If in doubt, delete it. Removing items from the \Run key does not actually delete files from the hard disk--it only prevents them from being run when the computer starts.
   
7. Press Delete, and then click Yes to confirm.
8. Navigate to and select the following key:
   
   HKEY_CLASSES_ROOT\exefile\shell\open\command
   
   CAUTION: The HKEY_CLASSES_ROOT key 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\.exe key.
   Do modify the HKEY_CLASSES_ROOT\exefile\shell\open\command subkey that is shown in the following figure:
   
   
   <<=== NOTE: This is the key that you need to modify.
   
   
9. Double-click the (Default) value in the right pane.
10. Delete the current value data, and then type: "%1" %* (That is, type the following characters: quote-percent-one-quote-space-percent-asterisk.)
    
    NOTE: The Registry Editor will automatically enclose the value within quotation marks. When you click OK, the (Default) value should look exactly like this: ""%1" %*"
    
11. Make sure you completely delete all value data in the command key prior to typing the correct data. If a space is left accidentally at the beginning of the entry, any attempt to run program files will result in the error message, "Windows cannot find .exe." or "Cannot locate C:\ <path and file name>." If this happens to you, start over at the beginning of this document, making sure to completely remove the current value data.
    
12. Restart the computer.

1. Start Windows Explorer.
2. Click the View menu (Windows 95/98) or the Tools menu (Windows Me), and then click Options or Folder Options.
3. Click the View tab, and uncheck "Hide file extensions for known file types."
4. Click Show all files, and click OK.

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 following:
   
   navidad*.exe
   
4. Click Find Now or Search Now.
5. Delete any copies that you find.
6. Delete the text navidad*.exe from the "Named" or "Search for..." box.
7. In the "Named" or "Search for..." box, type--or copy and paste--the following:
   
   winsvrc.* winsvic.* wintask.* emanuel*.exe
   
8. Click Find Now or Search Now.
9. Delete any files named Winsvrc.exe, Winsvrc.vxd, Winsvic.vxd, Wintask.exe, Wintask.vxd, or Emanuel.exe that you find.
   
   NOTE: If Norton AntiVirus is installed and running on this computer, you may be alerted that the files are infected when you complete the previous steps. If that happens, choose Delete, and ignore any subsequent Windows messages saying that the file cannot be deleted. (This is Windows alerting you that it cannot find the specified file. It cannot find the file because it has already been deleted by Norton AntiVirus.)
   
10. Close the Find or Search window.
11. Right-click the Recycle Bin icon on the Windows desktop, and click Empty Recycle Bin.
    

Revision History:

September 20, 2002. Downgraded from Category 3 to Category 2 based on decreased rate of submissions.

Write-up by: Eric Chien