W32.HLLW.Purol

Risk Level 1: Very Low

Discovered:
April 11, 2003
Updated:
February 13, 2007 11:45:35 AM
Type:
Worm
Systems Affected:
Windows 2000, Windows 95, Windows 98, Windows Me, Windows NT, Windows XP

SUMMARY


W32.HLLW.Purol is a worm that attempts to spread through file-sharing networks and to delete certain files from the infected computer.

The worm uses this icon:



to attempt to disguise itself as an ordinary zip file.

W32.HLLW.Purol is written in Microsoft Visual Basic (VB) and compressed with UPX. The VB run-time libraries must be installed for it to execute.

Antivirus Protection Dates

  • Initial Rapid Release version April 11, 2003
  • Latest Rapid Release version September 28, 2010 revision 054
  • Initial Daily Certified version April 11, 2003
  • Latest Daily Certified version September 28, 2010 revision 036
  • Initial Weekly Certified release date April 16, 2003
Click here for a more detailed description of Rapid Release and Daily Certified virus definitions.

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

Distribution

  • Distribution Level: Medium

TECHNICAL DETAILS


When W32.HLLW.Purol runs, it does the following:
  1. Attempts to delete all the files from the following folders:
    • C:\Progra~1\eSafe\Protect
    • C:\Progra~1\McAfee VirusScan
    • C:\Progra~1\NORTON~1
    • C:\Progra~1\Acceleration Software\Anti-Virus
    • C:\Progra~1\F-prot
    • C:\Progra~1\Mcafee
    • C:\Progra~1\Kasper~1
    • C:\Progra~1\Avpersonal
    • C:\Progra~1\Bullguard

  2. Copies itself as:
    • C:\Windows\Hwinfoq.com
    • C:\Windows\Lorupscr.scr
    • C:\Windows\Winstart32.exe

  3. Creates the folder, C:\Windows\MyShares, and copies the following files to that location:
    • C:\Windows\Temporary Internet Files\*.txt
    • C:\Documents And Settings\Local Settings\Temp\*.doc
    • \My Chat Logs\*.*
    • C:\Windows\*.pwl
    • C:\Windows\*.ini
    • C:\Windows\temp\*.Doc
    • C:\Windows\Temp\*.txt
    • C:\Windows\Temp\*.rtf

  4. Checks the following folders:
    • C:\Windows\Myshares
    • C:\Program Files\Icq\Shared Files
    • C:\Program Files\Bearshare\Shared
    • C:\Program Files\Morpheus\My Shared Folder
    • C:\Program Files\Edonkey2000\Incoming
    • C:\Program Files\Gnucleus\Downloads
    • C:\Program Files\Gnucleus\Downloads\Incoming
    • C:\Program Files\Kazaa\My Shared Folder
    • C:\Program Files\Kazaa Lite\My Shared Folder
    • C:\Program Files\Limewire\Shared

      Then, the worm copies itself to any of the folders that it finds.

  5. Adds the value:

    "Winstart"="c:\windows\winstart32.exe"

    to the following registry keys:

    HKEY_USERS\.DEFAULT\Software\Microsoft\Windows\CurrentVersion\
    RunServices
    HKEY_USERS\.DEFAULT\Software\Microsoft\Windows\CurrentVersion\Run


  6. Adds the following values:

    "ScreenSaverTimeOut"="300"
    "ScrnSAVE.EXE"="c:\windows\lorups~1.scr"
    "ScreenSaveActive"="1"

    to the registry key:

    HKEY_USERS\.DEFAULT\Control Panel\Desktop

  7. Adds the value:

    "HWINFOa"="c:\windowsHWINFOa.com"

    to the registry key:

    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion

  8. Adds the value:

    "Done"="True"

    to the registry key:

    HKEY_USERS\.DEFAULT\Software\Lorup

  9. Creates several entries in the following registry keys:

    HKEY_USERS\.DEFAULT\Software\Kazaa
    HKEY_USERS\.DEFAULT\Software\Kazaa lite
    HKEY_USERS\.DEFAULT\Software\Grokster
    HKEY_USERS\.DEFAULT\Software\Grokster lite
    HKEY_USERS\.DEFAULT\Software\iMesh
    HKEY_USERS\.DEFAULT\Software\iMesh lite

    to share the folder, C:\Windows\MyShares.

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.

REMOVAL


These instructions pertain to all current and recent Symantec antivirus products, including the Symantec AntiVirus and Norton AntiVirus product lines.
  1. Reverse the changes that the worm made to the registry, and then restart computer. Re-install Norton AntiVirus if necessary.
  2. Update the virus definitions.
  3. Run a full system scan and delete all the files detected as W32.HLLW.Purol.

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

1. Reversing the changes made 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 the specified keys only. Read the document, "How to make a backup of the Windows registry," for instructions.
  1. Click Start, and then click Run. (The Run dialog box appears.)

  2. Type regedit, and then click OK. (The Registry Editor opens.)

  3. Navigate to the key:

    HKEY_USERS\.DEFAULT\Software\Microsoft\Windows\CurrentVersion\Run

  4. In the right pane, delete the values:

    "Winstart"="c:\windows\winstart32.exe"

  5. Navigate to the key:

    HKEY_USERS\.DEFAULT\Software\Microsoft\Windows\CurrentVersion\
    RunServices


  6. In the right pane, delete the values:

    "Winstart"="c:\windows\winstart32.exe"

  7. Navigate to the key:

    HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run

  8. In the right pane, delete the values:

    "HWINFOa"="c:\windows\HWINFOa.com"

  9. Delete the following registry values:

    HKEY_USERS\.DEFAULT\Software\Lorup\Done                                                 True
    HKEY_USERS\.DEFAULT\Software\KAZAA\LocalContent\dir0                       012345:c:\windows\MyShares
    HKEY_USERS\.DEFAULT\Software\KAZAA lite\LocalContent\dir0                012345:c:\windows\MyShares
    HKEY_USERS\.DEFAULT\Software\Grokster\LocalContent\dir0                    012345:c:\windows\MyShares
    HKEY_USERS\.DEFAULT\Software\Grokster lite\LocalContent\dir0             012345:c:\windows\MyShares
    HKEY_USERS\.DEFAULT\Software\iMesh\Client\LocalContent\dir0             012345:c:\windows\MyShares
    HKEY_USERS\.DEFAULT\Software\iMesh lite\Client\LocalContent\dir0      012345:c:\windows\MyShares


  10. Exit the Registry Editor.

  11. Restart the computer.

  12. If the worm deleted Norton AntiVirus, re-install it.

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 here. For detailed instructions on how to download and install the Intelligent Updater virus definitions from the Symantec Security Response Web site, click here.

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.
  2. Run a full system scan.
  3. If any files are detected as infected with W32.HLLW.Purol, click Delete.