Threat Descriptons



Category :


Type :


Aliases :

Infis, WinNT/Infis, WinNT.Infis.4608


Infis is a memory resident virus. It can replicate under Windows NT 4.0 with Service Packs 2, 3, 4, 5, 6 installed. It does not work on systems running Windows 95/98, Windows 2000 or other versions of Windows NT.


Based on the settings of your F-Secure security product, it will either move the file to the quarantine where it cannot spread or cause harm, or remove it.

A False Positive is when a file is incorrectly detected as harmful, usually because its code or behavior resembles known harmful programs. A False Positive will usually be fixed in a subsequent database update without any action needed on your part. If you wish, you may also:

  • Check for the latest database updates

    First check if your F-Secure security program is using the latest updates, then try scanning the file again.

  • Submit a sample

    After checking, if you still believe the file is incorrectly detected, you can submit a sample of it for re-analysis.

    Note: If the file was moved to quarantine, you need to collect the file from quarantine before you can submit it.

  • Exclude a file from further scanning

    If you are certain that the file is safe and want to continue using it, you can exclude it from further scanning by the F-Secure security product.

    Note: You need administrative rights to change the settings.

Technical Details

The virus usually arrives in an infected EXE file and being run installs itself to system. The virus copies its body to INF.SYS file in Windows NT drivers folder WinNT\System32\Drivers. Then it creates a key with three subkeys in Windows System Registry:

 Type = 1
 - standard Windows NT driver
 Start = 2
- driver start mode
 ErrorControl = 1 - continue system loading on error in driver

As a result the virus in INF.SYS file will be activated every time the operating system starts. When INF.SYS file is activated the virus first infects Windows NT memory. When this is done the virus takes control over some Windows NT internal undocumented functions. The virus traps file opening routine and if any file is opened it checks file name and file's internal format and then calls his infection routine if PE EXE file is opened.

The virus infects only PE (Portable Executable) EXE-files except CMD.EXE (Windows NT command processor). When infecting the virus increases file length by the length of its "pure code" - 4608 bytes. The virus doesn't infect files twice. It recognizes already infected files by "date and time" stamp changed to -1 (FFFFFFFFh) value upon first infection.

The Infis virus does not have any destructive payload. However, it has bugs that could result in corrupting of some files upon infection. When a corrupted file is run it the standard Windows NT application error message is shown.

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