W95.MTX

Worm component
The worm component makes a copy of Wsock32.dll and names it Wsock32.mtx. The Send export function of this .mtx file is then modified to point to its own code. This allows the virus to mail a copy of the worm infected with this virus to the same person to whom the user sends an email message (using the same program).

Here is a list of file names that this virus might use when it sends the infected worm to other people. For those files with .pif extensions, the .pif extension might not be visible in your mail program.

I_wanna_see_you.txt.pif
Matrix_screen_saver.scr
Love_letter_for_you.txt.pif
New_playboy_screen_saver.scr
Bill_gates_piece.jpg.pif
Tiazinha.jpg.pif
Feiticeira_nua.jpg.pif
Geocities_free_sites.txt.pif
New_napster_site.txt.pif
Metallica_song.mp3.pif
Anti_cih.exe
Internet_security_forum.doc.pif
Alanis_screen_saver.scr
Reader_digest_letter.txt.pif
Win_$100_now.doc.pif
Is_linux_good_enough!.txt.pif
Qi_test.exe
Avp_updates.exe
Seicho_no_ie.exe
You_are_fat!.txt.pif
Free_xxx_sites.txt.pif
I_am_sorry.doc.pif
Me_nude.avi.pif
Sorry_about_yesterday.doc.pif
Protect_your_credit.html.pif
Jimi_hendrix.mp3.pif
Hanson.scr
F___ing_with_dogs.scr
Matrix_2_is_out.scr
Zipped_files.exe
Blink_182.mp3.pif

Wininit.ini is created by this component, which causes Wsock32.dll to be deleted and Wsock32.mtx to be renamed to Wsock32.dll. Wininit.ini executes after the computer is restarted. After Wininit.ini is created, this component runs the virus component.

NOTE: Norton AntiVirus will detect the Wininit.ini file that's created by W95.MTX as W95.MTX.INI.

Virus component
The virus component searches for specific antivirus programs running. If the virus finds one, the virus does not run. If the virus continues to run, it decompresses the worm component, drops a copy of it into the user's Windows directory (typically C:\Windows), and runs it. The name of this dropped file is Ie_pack.exe. After Ie_pack.exe is executed, it is renamed to Win32.dll.

The virus also drops Mtx_.Exe and runs it. This is a downloader program that goes to a specific Web site (i.am/[MATRIX]) where plug-ins for the virus are downloaded and executed. It searches for Win32 executables in the current directory, Windows directory, and the Temp directory. The file to be infected needs to have a size that is not divisible by 101, is greater than 8 KB in size, and has at least 20 import call instructions. If not, the file is not infected by the virus.

The virus also adds a registry entry that lets the downloader run automatically every time the system is started. The downloader is invisible in the Task List.

Recommendations

Symantec Security Response encourages all users and administrators to adhere to the following basic security "best practices":

• Use a firewall to block all incoming connections from the Internet to services that should not be publicly available. By default, you should deny all incoming connections and only allow services you explicitly want to offer to the outside world.
• 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.
• Ensure that programs and users of the computer use the lowest level of privileges necessary to complete a task. When prompted for a root or UAC password, ensure that the program asking for administration-level access is a legitimate application.
• Disable AutoPlay to prevent the automatic launching of executable files on network and removable drives, and disconnect the drives when not required. If write access is not required, enable read-only mode if the option is available.
• Turn off file sharing if not needed. If file sharing is required, use ACLs and password protection to limit access. Disable anonymous access to shared folders. Grant access only to user accounts with strong passwords to folders that must be shared.
• Turn off and remove unnecessary services. By default, many operating systems install auxiliary services that are not critical. These services are avenues of attack. If they are removed, threats have less avenues of attack.
• If a 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.
• Configure your email server to block or remove email that contains file attachments that are commonly used to spread threats, such as .vbs, .bat, .exe, .pif and .scr files.
• Isolate compromised computers quickly to prevent threats from spreading further. 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.
• If Bluetooth is not required for mobile devices, it should be turned off. If you require its use, ensure that the device's visibility is set to "Hidden" so that it cannot be scanned by other Bluetooth devices. If device pairing must be used, ensure that all devices are set to "Unauthorized", requiring authorization for each connection request. Do not accept applications that are unsigned or sent from unknown sources.
• For further information on the terms used in this document, please refer to the Security Response glossary.

Summary