Threat Explorer

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VBS.Lavra.Worm

VBS.Lavra.Worm

Discovered:
10 September 2002
Updated:
13 February 2007
Also Known As:
Worm.P2P.Lavra [AVP]
Systems Affected:
Windows

VBS.Lavra.Worm is a worm that attempts to spread across file-sharing networks such as KaZaA, Morpheus, BearShare, Grokster and ICQ. It disguises itself as a pornography-related program to trick users into downloading and opening it. The worm also attempts to delete files of various antivirus and firewall programs. VBS.Lavra.Worm is a Visual Basic Script (VBS) worm.

Antivirus Protection Dates

  • Initial Rapid Release version 10 September 2002
  • Latest Rapid Release version 28 September 2010 revision 054
  • Initial Daily Certified version 10 September 2002
  • Latest Daily Certified version 28 September 2010 revision 036
  • Initial Weekly Certified release date 11 September 2002
Click here for a more detailed description of Rapid Release and Daily Certified virus definitions.

When VBS.Lavra.Worm runs, it performs the following actions:

It displays this message:
Not a Win32 app.Error on module DllExec.

It copies itself as these files:
  • C:\Windows\MrsAnnitaBeta.vbs
  • C:\WinNT\MrsAnnitaBeta.vbs

To provide for replication across the file-sharing networks, the worm attempts to copy itself under different pornography-related file names into the following folders:
  • C:\Archiv~1\Morpheus\My Shared Folder
  • C:\Program FIles\Grokster\My Grokster
  • C:\Program FIles\Bearshare\Shared
  • C:\Program FIles\ICQ\shared files
  • C:\Program FIles\KaZaA\My Shared Folder

The worm attempts to disable some antivirus and firewall programs by deleting files from the following locations:
  • C:\Program Files\Grisoft\AVG6
  • C:\AntiViral Toolkit Pro
  • C:\Program Files\Command Software\F-PROT95
  • C:\Program Files\McAfee\VirusScan
  • C:\Program Files\Norton AntiVirus
  • C:\Toolkit\FindVirus
  • C:\Program Files\Panda Software\Panda Antivirus Titanium
  • C:\Program Files\Tiny Personal Firewall
  • C:\PC-Cillin 95
  • C:\PC-Cillin 97
  • C:\Program Files\Trend Micro\PC-cillin 2002
  • C:\Program Files\Zone Labs\ZoneAlarm
  • C:\Program Files\Tiny Personal Firewall\

Finally, the worm rewrites the C:\Autoexec.bat file with the commands that run the worm. The rewritten file is detected as Trojan Horse.

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.

NOTES:
  • These instructions are for all current and recent Symantec antivirus products, including the Symantec AntiVirus and Norton AntiVirus product lines.
  • If the worm has run, you may first need to reinstall your antivirus and firewall software.
  1. Update the virus definitions.
  2. Run a full system scan, and delete all files that are detected as VBS.Lavra.Worm or Trojan Horse.

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.
  2. Run a full system scan.
  3. If any files are detected as infected with VBS.Lavra.Worm or Trojan Horse, click Delete. On Windows 95/98/Me-based computers, restore the Autoexec.bat file from a clean backup, if necessary.


Writeup By: Serghei Sevcenco