W32.HLLW.Winevar

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Discovered: November 23, 2002
Updated: February 13, 2007 11:41:16 AM
Also Known As: W32/Korvar [McAfee], WORM_WINEVAR.A [Trend], I-Worm.Winevar [KAV]
Type: Worm
Systems Affected: Windows
CVE References: CVE-2000-1061 CVE-2001-0154


W32.HLLW.Winevar is a mass-mailing worm that disables some antivirus and firewall programs and drops and executes the W32.FunLove.4099 virus.

Symantec Security Response encourages you to block email attachments that have .pif or .ceo extensions.

W32.HLLW.Winevar arrives in an email that contains three attachments. The names are variable but they will have the format:

  • Win<several characters>.Txt (12.6 KB) Music_1.htm
  • Win<several characters>.Gif (120 Bytes) Music_2.ceo
  • Win<several characters>.pif

The .htm file exploits the Microsoft VM ActiveX Component vulnerability to register the .ceo extension as an executable file. The email message is formed to take advantage of the Incorrect MIME Header Can Cause IE to Execute E-mail Attachment vulnerability, but due to a bug in the code, the attachment will not run automatically. Please note that the .htm will be detected as JS.Exception.Exploit.

Antivirus Protection Dates

  • Initial Rapid Release version November 24, 2002
  • Latest Rapid Release version September 28, 2010 revision 054
  • Initial Daily Certified version November 24, 2002
  • Latest Daily Certified version September 28, 2010 revision 036
  • Initial Weekly Certified release date November 24, 2002

Click here for a more detailed description of Rapid Release and Daily Certified virus definitions.

Writeup By: Peter Ferrie

Discovered: November 23, 2002
Updated: February 13, 2007 11:41:16 AM
Also Known As: W32/Korvar [McAfee], WORM_WINEVAR.A [Trend], I-Worm.Winevar [KAV]
Type: Worm
Systems Affected: Windows
CVE References: CVE-2000-1061 CVE-2001-0154


When W32.HLLW.Winevar is first executed, it attempts to terminate and disable some antivirus and firewall products. This is achieved by listing all services and windows, and terminating any process or service whose name contains any of the following:

  • view
  • debu
  • scan
  • mon
  • vir
  • iom
  • ice
  • anti
  • fir
  • prot
  • secu
  • dbg
  • avk
  • pcc
  • spy

unless the name also contains any of these:
  • microsoft
  • ms
  • _np
  • r n
  • cicer
  • irmon
  • smtpsvc
  • moniker
  • office
  • program
  • explorewclass

After all processes and services have been checked, the worm adds a reference to itself to the registry.

Under Windows 95/98/Me, the worm adds or modifies one of these values:

(Default) Win<several characters>.pif
Win<several characters>  Win<several characters>.pif

to the registry key

HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\RunServices

Under all platforms the worm adds or modifies one of these values:

(Default)
Win<several characters>

to these registry keys:

HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run
HKEY_Current_User\Software\Microsoft\Windows\CurrentVersion\Run

Every time that the worm is executed, new data will be added to these values.

As a result, the worm runs each time that you start Windows.

After altering the registry, the worm copies itself as %system%\Win<several characters>.pif, and then executes it, passing as a parameter the current time in milliseconds. When this second instance of the worm gains control, it checks the elapsed time against the parameter that was passed. If more than 512 milliseconds have elapsed, then the worm displays the following message and activates its payload:




The payload runs a routine to terminate and disable antivirus and firewall products. This is done once every second, while the worm attempts to delete all files in all subfolders on the drive from which the worm was launched.

If the payload has not been activated, then the worm attempts to create the mutex

~~ Drone of StarCraft~~

If there is no active Internet connection, which the worm determines by attempting to download the web page at www.symantec.com, then the worm drops and runs the copy of W32.Funlove.4099 that the worm carries.

If there is an active internet connection, then the worm queries the registered organization and registered owner from the registry. If the registered organization value does not exist, then the worm will use "Trand Microsoft Inc.". If the registered owner value does not exist, then the worm will use the value "AntiVirus".

Next, the worm copies itself to the %desktop% folder as Explorer.pif.

Next, on each fixed drive on the local computer, the worm examines all files in all subfolders, looking for .htm and .dbx files. If the name of any subfolder contains any of these strings:
  • antivirus
  • cillin
  • nlab
  • vacc

then the worm deletes all files in all subfolders under these subfolders. These names correspond to popular antivirus software in Korea, China, and Japan.

If any .htm or .dbx files are found, then the worm looks inside them for email addresses. For each email address that does not contain "@microsoft.," if the address has not already been sent email, the worm sends itself to that address. The worm saves the list of recipients in the registry under HKEY_CLASSES_ROOT\Software\Microsoft\DataFactory. The list is kept only for the current session, and is deleted every time that the worm is restarted. The worm uses its own SMTP client engine to send email, and uses DNS lookup to determine the mail server from the recipient's domain name.

The email will be in the form:

From: <registered owner or "AntiVirus"> <recipient's e-mail address>
To: <recipient's email address>
Subject:

Re: AVAR(Association of Anti-Virus Asia Reseachers)

or

N`4?<registered organisation or "Trand Microsoft Inc.">

Message body:

AVAR(Association of Anti-Virus Asia Reseachers) - Report.
Invariably, Anti-Virus Program is very foolish.

or

<registered owner> - <registered organization>

If no email is sent, either because no .htm or .dbx files were found, or because of some error, then the worm displays the message box shown above.

After attempting to send email, then worm attempts to perform a denial of service against www.symantec.com by requesting the default page as often as possible.

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.

Writeup By: Peter Ferrie

Discovered: November 23, 2002
Updated: February 13, 2007 11:41:16 AM
Also Known As: W32/Korvar [McAfee], WORM_WINEVAR.A [Trend], I-Worm.Winevar [KAV]
Type: Worm
Systems Affected: Windows
CVE References: CVE-2000-1061 CVE-2001-0154


NOTES:

  • These instructions are for all current and recent Symantec antivirus products, including the Symantec AntiVirus and Norton AntiVirus product lines.D
  • Due to the destructive nature of W32.HLLW.Winevar, in most cases, neither the tool or the manual removal instructions will work if the infected computer has been restarted. Once the computer is restarted after infection, the file deletion payload is activated and critical system files may be deleted. In this situation, you will have to first restore the deleted files from a clean backup or reinstall them.

CAUTION: If you suspect that the computer is infected with this threat, do not turn off or restart the computer until you have removed W32.HLLW.Winevar

Removal using the removal tool
Symantec Security Response has provided a free tool to remove infections of W32.HLLW.Winevar and W32.Funlove.4099. This is the easiest way to do this. For complete instructions on how to obtain and use the W32.HLLW.Winevar/W32.Funlove.4099 Removal Tool , click here .


Manual removal
  1. Update the virus definitions.
  2. Run a full system scan, and delete all files that are detected as W32.HLLW.Winevar, W32.FunLove.4099, or JS.Exception.Exploit.
  3. Reverse the changes that it made to the registry.

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 once 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 W32.HLLW.Winevar, W32.FunLove.4099, or JS.Exception.Exploit., click Delete.

To delete the values from 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 only the keys that are specified. Read the document How to make a backup of 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 each of these registry keys:

    HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\RunServices

    HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run

    HKEY_Current_User\Software\Microsoft\Windows\CurrentVersion\Run
  4. Look for any of these (or similar) values and delete them if found:

    (Default) Win<several characters>.pif

    Win<several characters>  Win<several characters>.pif
  5. Exit the Registry Editor.


Writeup By: Peter Ferrie