Threat Descriptons



Category :


Type :


Aliases :

Backdoor.IE_Patch, PHO.EXE


The 'Backdoor.IE_Patch' was first reported in March 1999. The PHO.EXE is originally used to spread the backdoor (i.e. hacker's remote access tool) files, but the file name could be different. The dropper is pretending to be a broken self-extracting ZIP archive. It even has a WinZip archive icon.


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

When PHO.EXE file is run it displays a messagebox with the following text:

Cannot open file: it does not apear to be a valid archive.
If you downloaded this file, try downloading the file again.
Please press F1 for help.

At the same time the dropper writes 3 files to \WINDOWS\SYSTEM directory: ADVAPI.DLL, ADVAPI32.EXE and ADVCCAPI.DLL. Then the dropper modifies SYSTEM.INI file. It adds a string 'ADVAPI.DLL' to 'DRIVERS=' string, so that ADVAPI.DLL will be run during next Windows startup.

Actually ADVAPI.DLL is only used to start ADVAPI32.EXE that will remain active all Windows session. This file is the server part of IE_Patch backdoor. It provides access to infected system for hackers having the client part of this backdoor.

Capabilities of IE_Patch backdoor include sending and receiving data (files), monitoring of existing application windows, listening to keystrokes. The backdoor has an empty email form inside.

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