W32.HLLW.Winevar

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.

Summary