Trojan:W32/Fixer
Summary
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.
Removal
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 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]
Activity
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
- 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:
- https://www.filefixpro.com/[...]/download.php
The downloaded program is a scanner that will show a screen like below:
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