VBS.Davinia.B

VBS.Davinia.B is an email worm that mails a message written in HTML to everyone in your Microsoft Outlook address book.

The message has no subject line and appears blank, but it contains HTML code that starts Internet Explorer and attempts to download and open a Microsoft Word 2000 document.

NOTE: The Word 2000 document has been removed from the Web server, so it cannot be downloaded, and the worm no longer operates properly.

The Word 2000 document contains a macro that does the following:

1. Performs the mass mailing using Outlook.
2. Creates a Visual Basic Script (VBS) file on the computer.
3. The VBS file is executed after the computer is restarted; it then overwrites and renames all files on the local and mapped drives.

Type:	Macro, Worm
Infection Length:	3409 bytes

Virus Definitions (Intelligent Updater) February 07, 2001

Wild Number of infections: 0 - 49 Number of sites: 0 - 2 Geographical distribution: Low Threat containment: Easy Removal: Moderate

Threat Metrics Wild: Low Damage: Medium Distribution: Medium

Damage

• Payload Trigger: Opening the Document
• Payload:
  • Large scale e-mailing: Emails a message with an HTML body that opens a viral URL to all addresses in the Outlook Address book
  • Modifies files: Overwrites all HTML and HTM files

Distribution

• Subject of email: No Subject

The worm arrives as an HTML email message. The subject and the body appear blank. The worm can only properly operate if you are using Microsoft Outlook without the Office 2000 UA Control patch. When reading the message, the HTML code will launch Internet Explorer. Internet Explorer will attempt to download and open a Word 2000 document.

The Word 2000 document contains a macro, which does the following:

1. Creates the \Windows\System\Littledavinia.vbs file.
2. Adds the value:
   
   Davinia         \Windows\System\Littledavinia.vbs
   
   to the following registry key:
   
   HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run
   
   This causes the file to be run when Windows starts.
   
3. The macro sends an HTML email message to all contacts in the Microsoft Outlook address book. This is recorded in the registry so that they are not emailed again.
4. The next time that the computer is restarted, the VBS file is executed. The VBS file first modifies the start page of Internet Explorer.
5. It then adds the value:
   
   Davi        littledavinia.html
   
   to the following key:
   
   HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run
   
6. The worm searches for all files on local and mapped drives and overwrites the files with HTML code. The HTML code displays a message that is customized with your name and email address.
7. The worm also creates the file \Windows\System\Littledavinia.html with the same code. This is executed the next time Windows is restarted.

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.

To recover from this infection you need to:

• Edit the registry \Run key to remove the values that refer to littledavinia.
• Scan for viruses and delete infected files.
• Replace overwritten files.

1. Click Start, and click Run. The Run dialog box appears.
2. Type regedit and then click OK. The Registry Editor opens.
3. Navigate to the following subkey:
   
   HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run
   
4. In the right pane, look for the following values:
   
   Davinia         \Windows\System\Littledavinia.vbs
   Davi            littledavinia.html
   
5. Select one, press Delete, and then click Yes to confirm. Repeat for the other one.
6. Click Registry, and click Exit to save the changes and close the Registry Editor.

1. Start Norton AntiVirus (NAV), and make sure that it is set to scan all files.
2. Run a full system scan.
3. Delete any files that are detected as infected with Davinia.B.

Write-up by: Douglas Knowles