Trojan:W32/Fixer, Trojan-Ransom.Win32.Fixer.a, Trojan.Generic.1582276


Trojan:W32/Fixer is a malicious program that demands a ransom from the user by encrypting and disabling documents and media files. The only way to decrypt the files is by purchasing a program being offered by the malware author(s). As such, this malware is a type of ransomware. The details below apply to the Trojan:W32/Fixer.A variant.

Automatic action

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.

Suspect a file is incorrectly detected (a False Positive)?

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 detection database 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.

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Technical Details

The trojan's main component is a DLL that is dropped to:

  • %system%\fpfstb.dll

This DLL is injected into almost all running processes. It is not injected into some executables, including:

  • smss.exe
  • csrss.exe
  • winlogon.exe

It adds a launchpoint in the registry as below:

  • HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Windows AppInit_DLLs = "%system%\fpfstb.dll"

It creates these registries probably as infection markers:

  • HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\WOW\keyboard is_installed = [random string]
  • HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\WOW\keyboard id = [random string]


Once installed, the DLL encrypts files with the following extensions to disable them :

  • ppsm
  • ppsx
  • ppam
  • potm
  • potx
  • pptm
  • pptx
  • xlam
  • xlsb
  • xltm
  • xltx
  • xlsm
  • xlsx
  • dotm
  • dotx
  • docm
  • docx
  • pst
  • mdb
  • wma
  • mp3
  • png
  • jpeg
  • jpg
  • pdf
  • ppt
  • xls
  • doc

Any newly created files on the system that use one of the extensions listed above are also encrypted.When user tries to open the encrypted files a screen like below is shown:

It also shows a popup like below at the bottom right corner on the system tray :

The only way for users to fix the so-called corrupted files is to purchase the FileFixPro program. If the "repair file" option is selected, user will be directed to this site:


The downloaded program is a scanner that will show a screen like below: