W32.HLLP.Sharpei@mm

SUMMARY

W32.HLLP.Sharpei@mm is a virus that targets .exe files under the Microsoft .NET Framework. The replication code of the virus is written in C# and compiled to MSIL. The virus also mass emails itself to all contacts in the Microsoft Outlook address book by using a VBS component. The attachment is MS02-010.exe.

Protection

• Virus Definitions (LiveUpdate™ Weekly) February 27, 2002
• Virus Definitions (Intelligent Updater) February 27, 2002

Threat Assessment

Wild

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

Damage

• Damage Level: Low
• Large Scale E-mailing: Yes
• Modifies Files: Yes

Distribution

• Distribution Level: Medium
• Subject of Email: Important: Windows update
• Name of Attachment: MS02-010.exe
• Size of Attachment: 12,288

TECHNICAL DETAILS

The virus arrives as an email message that has the following characteristics:

Subject : Important: Windows update

Message: Hey, at work we are applying this update because it makes Windows over 50% faster and more secure. I thought I should forward it as you may like it.

Attachment: Ms02-010.exe

When the attachment is executed, the virus does the following:

It makes a copy of itself as C:Ms02-010.exe.

It drops the file Sharp.vbs, which then performs the mass-mailing routine, sending the previously described message. Sharp.vbs then deletes itself.

NOTE: Even if you have not updated to the virus definition set that includes detection for W32.HLLP.Sharpei@mm, Sharp.vbs will be detected heuristically by Norton AntiVirus as Bloodhound.VBS.Worm. Once you have updated to this definition set, it will be detected as W32.HLLP.Sharpei@mm.

After the messages are successfully sent, they are deleted from the Outlook Sent folder. As a result, you will not see the messages in Outlook. This is an attempt to hide its activity.

If Mscoree.dll is found in the System folder, the virus creates Cs.exe in the Windows folder, and then executes it. The virus assumes that this library is installed only when the Microsoft .NET Framework is installed. Cs.exe is a .NET executable that is written in C# and runs only in the .NET Framework.

Finally Ms02-010.exe creates the following key in the registry:

HKEY_LOCAL_MACHINESoftwareSharp

with a string value set to the path of the .exe that was run. This is used later as a reference from Cs.exe to the executed application. This portion of the virus code is Intel assembly, which can run on all Intel-based Win32 systems.

NOTE: In some cases, this key will already exist, having been installed by a legitimate program, rather than the virus

Cs.exe runs in the .NET Framework and looks for the "Sharp" key in the registry to get a path to the application that executed it. This portion of the code is a complete prepending virus logic written in C#. The virus copies the complete contents of Ms02-010.exe to the front of .NET executables in the Program Files and Windows folders.

When an infected executable is run, it attempts to mail the virus again and looks for other files to infect; it also executes the host program after itself whenever possible. During this process, the virus uses temporary file names such as Hostcopy.exe and Temp.exe, which are then deleted.

The virus portion also creates another Sharp.vbs file, which contains code to only display a message. This file is created in the Windows Startup folder, so that the message appears when you start Windows.



Cs.exe attempts to handle some exceptions, but in our test environment it produced .NET Framework error messages. However, the virus was able to infect .NET files on the system.

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

Delete all files that are detected as W32.HLLP.Sharpei@mm and remove the value that it added to the registry.

1. Obtain the most recent virus definitions. There are two ways to do this:
   • Run LiveUpdate. LiveUpdate is the easiest way to obtain virus definitions. These virus definitions have undergone full quality assurance testing by Symantec Security Response and 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 have undergone full quality assurance testing by Symantec Security Response. They 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.
     
2. Start Norton AntiVirus (NAV), and make sure that NAV is configured to scan all files. For instructions on how to do this, read the document How to configure Norton AntiVirus to scan all files.
3. Run a full system scan.
4. Write down the file names of all files that are detected as W32.HLLP.Sharpei@mm, and then delete them.

To edit the registry:

CAUTION: We strongly recommend 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 back up 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 following key:
   
   HKEY_LOCAL_MACHINESoftwareSharp
   
4. In the right pane, delete any values that refer to the file that was detected as infected by W32.HLLP.Sharpei@mm.
5. Click Registry, and click Exit.