Discovered: February 04, 2009
Updated: June 27, 2013 1:49:23 PM
Also Known As: W32/Virut.n [McAfee], PE_VIRUX.A [Trend]
Type: Virus
Infection Length: 17,044 bytes
Systems Affected: Windows

W32.Virut.CF is a virus that infects .exe and .scr files on the compromised computer.

For more information, please read the following:

Symantec Endpoint Protection – Application and Device Control
Symantec Security Response has developed an Application and Device Control (ADC) Policy for Symantec Endpoint Protection to protect against the activities associated with this threat. ADC policies are useful in reducing the risk of a threat infecting a computer, the unintentional removal of data, and to restrict the programs that are run on a computer.

This particular ADC policy can be used to help combat an outbreak of this threat by slowing down or eliminating its ability to spread from one computer to another. If you are experiencing an outbreak of this threat in your network, please download the policy .

To use the policy, import the .dat file into your Symantec Endpoint Protection Manager. When distributing it to client computers, we recommend using it in Test (log only) mode initially in order to determine the possible impacts of the policy on normal network/computer usage. After observing the policy for a period of time, and determining the possible consequences of enabling it in your environment, deploy the policy in Production mode to enable active protection.

For more information on ADC and how to manage and deploy them throughout your organization, please refer to the Symantec Endpoint Protection Administration Manual (PDF).

Note: The ADC policies developed by Security Response are recommended for use in outbreak situations. While useful in such situations, due to their restrictive nature they may cause disruptions to normal business activities.

Antivirus Protection Dates

  • Initial Rapid Release version February 02, 2009 revision 036
  • Latest Rapid Release version January 14, 2020 revision 025
  • Initial Daily Certified version February 02, 2009 revision 064
  • Latest Daily Certified version January 13, 2020 revision 003
  • Initial Weekly Certified release date February 04, 2009

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

Technical Description

When the virus executes, it attempts to infect any file accessed with the following extensions:

  • .exe
  • .scr

The threat does not infect files starting with the following strings:
  • OTSP
  • WC32
  • WCUN
  • WINC

The virus also attempts to infect files with the following extensions by injecting an iframe in to the body of each file:
  • .htm
  • .html
  • .php
  • .asp

The above iframe redirects the browser on the computer to the following location:

It creates the following event so that only one instance of the threat is running on the compromised computer:

The virus then modifies the hosts file by prepending the following strings to its body:

It then opens a back door by joining a channel controlled by a remote attacker on one of the following IRC servers:
  • on TCP port 80
  • on TCP port 80

The remote attacker may use the following nick name:

It may use the following registry entry in binary format in order to decode an unknown server name and port number:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\"UpdateHost" = "[BINARY VALUE]"

The threat disables Windows File Protection in order to infect files on the computer.

It also modifies the following registry subkey in order to add a firewall exception:

The virus also attempts to download files on the compromised computer.


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.


You may have arrived at this page either because you have been alerted by your Symantec product about this risk, or you are concerned that your computer has been affected by this risk.

Before proceeding further we recommend that you run a full system scan . If that does not resolve the problem you can try one of the options available below.

If you are a Norton product user, we recommend you try the following resources to remove this risk.

Removal Tool

If you have an infected Windows system file, you may need to replace them using from the Windows installation CD .

How to reduce the risk of infection
The following resources provide further information and best practices to help reduce the risk of infection.

If you are a Symantec business product user, we recommend you try the following resources to remove this risk.

Identifying and submitting suspect files
Submitting suspicious files to Symantec allows us to ensure that our protection capabilities keep up with the ever-changing threat landscape. Submitted files are analyzed by Symantec Security Response and, where necessary, updated definitions are immediately distributed through LiveUpdate™ to all Symantec end points. This ensures that other computers nearby are protected from attack. The following resources may help in identifying suspicious files for submission to Symantec.

Removal Tool

If you have an infected Windows system file, you may need to replace them using from the Windows installation CD .

How to reduce the risk of infection
The following resource provides further information and best practices to help reduce the risk of infection.
Protecting your business network

The following instructions pertain to all current Symantec antivirus products.

1. Performing a full system scan
How to run a full system scan using your Symantec product

2. Restoring settings in the registry
Many risks make modifications to the registry, which could impact the functionality or performance of the compromised computer. While many of these modifications can be restored through various Windows components, it may be necessary to edit the registry. See in the Technical Details of this writeup for information about which registry keys were created or modified. Delete registry subkeys and entries created by the risk and return all modified registry entries to their previous values.

3. Restore unrepairable files
In cases of unrepairable and compromised files, users should restore the unrepairable files from a backup that is known to be clean.

The Windows Recovery Console can be useful for this to prevent potential reinfection:

There are several ways to do this depending on the types of backups available:

    In the case of Windows system files that are marked as unrepairable, users may also restore clean versions of a Windows executable from their install disks.

    In the case of third-party software, users may restore clean versions of unrepairable files from:
    • Backups taken from the company website
    • Backups from the original install media
    • Backups received from the company directly etc.

    Writeup By: Mircea Ciubotariu