W32.Yenik.A@mm

SUMMARY

W32.Yenik.A@mm is a worm that attempts to email itself to the addresses found in the Windows address book. The email attachment will have a variable subject and variable attachment name. The attachment will have a .exe file extension. It will also attempt to spread through file-sharing programs, such as KaZaA, Morpheus, eMule, eDonkey, BearShare, and Grokster, as well as ICQ.

This threat is written in C and is packed with UPX.

Protection

• Virus Definitions (LiveUpdate™ Weekly) February 11, 2004
• Virus Definitions (Intelligent Updater) February 10, 2004

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: Attempts to send itself to all the entires in the Windows Address Book.

Distribution

• Distribution Level: High
• Subject of Email: Variable.
• Name of Attachment: Variable with .exe file extension.
• Size of Attachment: 18,432 bytes
• Target of Infection: Attempts to spread through file-sharing programs, such as KaZaA, Morpheus, eMule, eDonkey, BearShare, and Grokster, as well as ICQ.

TECHNICAL DETAILS

This worm will not function as intended if the Updater.exe file is not located in the %System% folder.

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

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When W32.Yenik.A@mm is executed, it performs the following actions:

1. Attempts to make a copy of %System%Updater.exe in the current working directory (the directory in which the file was executed) as one of the following file names:
   
   • NewVirusCleaner.exe
   • Win98Security.exe
   • Patcher.exe
   • PrivateMessage.exe
   • FreeAntivirus.exe
   • InternetExplorerSecurity.exe
   • VirusHunherII.exe
   • W32-Myd00m_Blocker.exe
   • WinXP-SP1.exe
     
     For example, if the file arrived in the default Kazaa-shared folder (C:Program FilesKazaaMy Shared Folder) and was executed from that folder, it would attempt to locate the %System%Updater.exe file, and then copy it to C:Program FilesKazaaMy Shared Folder as one of the names above.
     
     
2. The worm will use the SMTP server and account information from the registry key:
   
   HKEY_CURRENT_USERSoftwareMicrosoftInternet Account ManagerAccounts
   
   to email itself to all the addresses in the Windows Address Book.
   
   
3. The subject, attachment, and message body varies, and will be temporarily stored in a text file named Yeni.txt, located in the current working directory. The email will have the following characteristics:
   
   Subject: One of the following:
   
   • Big Virus Cleaner Tools
   • Win98 Security Tools
   • New Big Patcher
   • New Private Message
   • Free Antivirus
   • Internet Explorer Security Bug Fix
   • Virus Hunter in your box
   • No Virus and New Life
   • New Security Patcher
     
     Body: One of the following:
     
   • What are Viruses, Trojan Horses and Worms? "Though these terms are often used interchangeably, they refer to different types of "malicious computer programs.
   • Guide to Online Security "Protecting your privacy and information online is extremely important to Yahoo!. We are " constantly evaluating our security technologies to ensure we are taking every reasonable "step to protect your personal information.
   • Disabling System Restore (Windows Me/XP) "If you are running Windows Me or Windows XP, we recommend that you temporarily turn off System" Restore. Windows Me/XP uses this feature, which is enabled by default, to restore the files on your "computer in case they become damaged. If a virus, worm, or Trojan infects a computer, System "Restore may back up the virus, worm, or Trojan on the computer.
     
     Attachment: Will be one of the file names listed in step 1.
     
     
4. Then, the worm will attempt to copy itself to each of the following folders (if present):
   
   • C:Program FilesMorpheusMy Shared Folder
   • C:Program FileseMuleIncoming
   • C:Program FileseDonkey2000Incoming
   • C:Program FilesBearshareShared
   • C:Program FilesGroksterMy Grokster
   • C:Program FilesICQShared Folder
   • C:Program FilesKazaa Lite K++My Shared Folder
   • C:Program FilesKazaa LiteMy Shared Folder
   • C:Program FilesKazaaMy Shared Folder
     
     as all of the following file names:
     
     
   • DivX Pro.exe
   • ICQ Hacker.exe
   • Half Life 2 Original KeyGen.exe
   • GTA Keygen.exe
   • Windows Password Cracker.exe
   • Matrix Screen Saver.exe
   • NetBIOS Hacker.exe
   • New Exploit.exe
   • Kaspersky Anti-Hacker.exe
   • Linux Kernel Hacker.exe
   • Ftp Hacker.exe
   • PopStar-Firdevs.mp3.exe
   • PopStar-Abidin.mp3.exe
   • PopStar-Bayhan.mp3.exe
   • New Keylogger.exe
   • Hotmail Hacker.exe

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

The following instructions pertain to all current and recent Symantec antivirus products, including the Symantec AntiVirus and Norton AntiVirus product lines.

1. Disable System Restore (Windows Me/XP).
2. Update the virus definitions.
3. Run a full system scan and delete all the files detected as W32.Yenik.A@mm.

For specific details on each of these steps, read the following instructions.

1. Disabling System Restore (Windows Me/XP)
If you are running Windows Me or Windows XP, we recommend that you temporarily turn off System Restore. Windows Me/XP uses this feature, which is enabled by default, to restore the files on your computer in case they become damaged. If a virus, worm, or Trojan infects a computer, System Restore may back up the virus, worm, or Trojan on the computer.

Windows prevents outside programs, including antivirus programs, from modifying System Restore. Therefore, antivirus programs or tools cannot remove threats in the System Restore folder. As a result, System Restore has the potential of restoring an infected file on your computer, even after you have cleaned the infected files from all the other locations.

Also, a virus scan may detect a threat in the System Restore folder even though you have removed the threat.

For instructions on how to turn off System Restore, read your Windows documentation, or one of the following articles:

• "How to disable or enable Windows Me System Restore"
• "How to turn off or turn on Windows XP System Restore"

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Note: When you are completely finished with the removal procedure and are satisfied that the threat has been removed, re-enable System Restore by following the instructions in the aforementioned documents.

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For additional information, and an alternative to disabling Windows Me System Restore, see the Microsoft Knowledge Base article, "Antivirus Tools Cannot Clean Infected Files in the _Restore Folder," Article ID: Q263455.

2. Updating the virus definitions
Symantec Security Response fully tests all the virus definitions for quality assurance before they are posted to our servers. There are two ways to obtain the most recent virus definitions:

• Running LiveUpdate, which is the easiest way to obtain virus definitions: These virus definitions are posted to the LiveUpdate servers once each week (usually on Wednesdays), unless there is a major virus outbreak. To determine whether definitions for this threat are available by LiveUpdate, refer to the Virus Definitions (LiveUpdate).
• Downloading the definitions using the Intelligent Updater: The Intelligent Updater virus definitions are posted on U.S. business days (Monday through Friday). You should download the definitions from the Symantec Security Response Web site and manually install them. To determine whether definitions for this threat are available by the Intelligent Updater, refer to the Virus Definitions (Intelligent Updater).
  
  The Intelligent Updater virus definitions are available: Read "How to update virus definition files using the Intelligent Updater" for detailed instructions.

3. Scanning for and deleting the infected files

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