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Discovered: February 21, 2000
Updated: February 13, 2007 11:32:42 AM
Also Known As: WNT.Infis.4608.B
Type: Virus
Systems Affected: Windows

The WNT.Infis.4608 virus was updated to support the OEM version of Windows 2000 build 2195, and also fixes a few small bugs in the original release. This update, W2K.Infis.4608, is the first known virus to run in Kernel-mode under Windows 2000 (its predecessor was the first known Windows NT Kernel-mode virus).

Antivirus Protection Dates

  • Initial Rapid Release version March 01, 2000
  • Latest Rapid Release version September 28, 2010 revision 054
  • Initial Daily Certified version March 01, 2000
  • Latest Daily Certified version September 28, 2010 revision 036
  • Initial Weekly Certified release date March 01, 2000

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

Writeup By: Peter Szor

Discovered: February 21, 2000
Updated: February 13, 2007 11:32:42 AM
Also Known As: WNT.Infis.4608.B
Type: Virus
Systems Affected: Windows

W2K.Infis is a memory resident parasitic Windows 2000 Kernel-mode driver virus. It operates under Windows 2000 only and will likely fail under the first service pack. The virus does not have any payload.

The virus executes while the user is logged on with Administrator privileges (or equivalent) so that it can install its kernel mode component. Without these priveleges, the virus is unable to install itself or infect other files because it does not contain a User mode replication component.

The virus creates a registry entry named HKLM\System\CurrentControlSet\Services\inf, and also creates a file named inf.sys in this directory: \Winnt\System32\Drivers.

The inf.sys file is a native Windows 2000 Kernel-mode driver, and its size is 4608 bytes. Once the system is restarted, the virus driver (inf.sys) is loaded into memory automatically.

The virus hooks a Kernel mode file open API using a nonstandard method and infects the 32-bit Portable Executable applications with an .exe file name that are accessed "on the fly". The virus will not infect cmd.exe, and is also unable to infect a file that has a read-only attribute. The virus fails to infect some applications properly, and as a result some of the application fails to execute properly. This makes the virus easily noticeable on a system.

The virus driver can be disabled manually by going to the Computer Management\Device Manager entry. The View options need to be changed to Show hidden devices and Device by connection type should be selected in order to see the inf driver name:

Once the driver is disabled, the infected files should be detected and replaced from clean backups.


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 Szor