W32.Deltad.A@mm

SUMMARY

W32.Deltad.A@mm is a mass-mailing worm that is written in a high-level language. The actual mass-mailing is performed by a VBS script that is inserted on the system. The e-mail message has the following characteristics:
Subject: SAP UPDATE
Attachment: WWW.DGSAP.DELTADG.COM.EXE

W32.Deltad.A@mm attempts to open the Admin$ share.

The executable part of this worm is detected as W32.Deltad.A@mm, and the VBS script is detect as VBS.Deltad.A@mm.

NOTE: Definitions dated before September 18, 2002, detect the VBS script as BloodHound.VBS.Worm.

Protection

• Virus Definitions (LiveUpdate™ Weekly) September 18, 2002
• Virus Definitions (Intelligent Updater) September 18, 2002

Threat Assessment

Wild

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

Damage

• Damage Level: Medium
• Releases Confidential Info: Opens the Admin$ share. This can pontentially give a hacker control over the system.

Distribution

• Distribution Level: High
• Subject of Email: SAP Update
• Name of Attachment: WWW.Dgsap.Deltadg.com.exe
• Size of Attachment: 221 KB

TECHNICAL DETAILS

When W32.Deltad.A@mm is executed, it does the following.

First, it inserts the following files on the system:

• %system%Server.exe
• %system%System.txt.vbs
• %windir%Server.exe
• %windir%System.txt.vbs

NOTES:

• %windir% is a variable. The worm locates the Windows installation folder (by default this is C:Windows or C:Winnt) and copies the files to that location.
• %system% is a variable. The worm locates the System folder and copies the files to that location. By default this is C:WindowsSystem (Windows 95/98/Me), C:WinntSystem32 (Windows NT/2000), or C:WindowsSystem32 (Windows XP).

The worm may also insert a file named WWW.Dgsap.Deltadg.com.exe on the Windows desktop and directly under the root of drive C.

Next, the worm modifies or adds many keys in the Windows registry.

It adds these values:

winserver %system%Server.txt.vbs
server %system%Server.exe

to the key

HKEY_LOCAL_MACHINESoftwareMicrosoftWindowsCurrentVersionRun

and the value

server %windir%Server.exe

to the key

HKEY_LOCAL_MACHINESoftwareMicrosoftWindowsCurrentVersionRunServices

As a result of these additions, the worm runs each time that you start Windows.

It also modifies several registry subkeys under the key

HKEY_LOCAL_MACHINESoftwareMicrosoftWindowsCurrentVersionNetworkLanManAdmin$

The modifications to these keys cause the Windows folder to be shared as Admin$ with a password.

W32.Deltad.A@mm also attempts to lower the security settings for Internet Explorer and Microsoft Outlook by modifying registry keys that belonging to these programs.

After all of these actions have occurred, the worm attempts to open a Web page in Internet Explorer. Because the worm runs every time that the computer is started, an Internet Explorer window with this Web page opens each time that you start Windows.

After you restart the computer, this worm attempts to email itself to all contacts in the Microsoft Outlook Address Book. The email routine is carried out by the System.txt.vbs script that was inserted on the system. The e-mail message has the following characteristics:
Subject:
SAP UPDATE
Message Body:
All:
Please update your system.
DGSAP
Attachment:
WWW.DGSAP.DELTADG.COM.EXE

The script sets a registry key after the email routine has been completed. Therefore, it attempts to do this only one time.

NOTE: Definitions dated before September 18, 2002, detect the VBS script as BloodHound.VBS.Worm.

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

NOTE: These instructions are for all current and recent Symantec antivirus products, including the Symantec AntiVirus and Norton AntiVirus product lines.

1. Update the virus definitions.
2. Run a full system scan, and delete all files that are detected as W32.Deltad.A@mm or VBS.Deltad.A@mm.
3. Delete the values
   
   winserver %system%Server.txt.vbs
   server %system%Server.exe
   
   from the registry key
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRun
   
4. Delete the value
   
   server %windir%Server.exe
   
   from the registry key
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRunServices.
   
5. Reset the Admin$ share as you want, and verify that the security settings for Internet Explorer and Microsoft Outlook are correct.

For details on how to do this, read the following instructions.

To update the virus definitions:
All virus definitions receive full quality assurance testing by Symantec Security Response before being posted to our servers. There are two ways to obtain the most recent virus definitions:

• Run LiveUpdate, which is the easiest way to obtain virus definitions. These virus definitions are posted to the LiveUpdate servers one time each week (usually Wednesdays) unless there is a major virus outbreak. To determine whether definitions for this threat are available by LiveUpdate, look at the Virus Definitions (LiveUpdate) line at the top of this write-up.
• Download the definitions using the Intelligent Updater. Intelligent Updater virus definitions are posted on U.S. business days (Monday through Friday). They must be downloaded from the Symantec Security Response Web site and installed manually. To determine whether definitions for this threat are available by the Intelligent Updater, look at the Virus Definitions (Intelligent Updater) line at the top of this write-up.
  
  Intelligent Updater virus definitions are available here. For detailed instructions on how to download and install the Intelligent Updater virus definitions from the Symantec Security Response Web site, click here.

To scan for and delete the infected files:

1. Start your Symantec antivirus program, and make sure that it is configured to scan all files.
   • Norton AntiVirus consumer products: Read the document How to configure Norton AntiVirus to scan all files.
   • Symantec enterprise antivirus products: Read the document How to verify 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.Deltad.A@mm or VBS.Deltad.A@mm, click Delete.

To delete the values that the worm added to the registry:

CAUTION: Symantec strongly recommends that you back up the registry before you make any changes to it. Incorrect changes to the registry can result in permanent data loss or corrupted files. Modify only the keys that are specified. Read the document How to make a backup of the Windows registry for instructions.

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 key
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRun
   
4. In the right pane, delete the values
   
   winserver %system%Server.txt.vbs
   server %system%Server.exe
   
5. Navigate to the key
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRunServices
   
6. In the right pane, delete the value
   
   server %windir%Server.exe
   
7. Exit the Registry Editor.

To reset the Admin$ share and verify security settings:
The procedure for doing this depends on your versions of Window, Internet Explorer, and Microsoft Outlook. Please see the operating system and program documentation for instructions on how to do this.