Trojan:W32/Fixer

Classification

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

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
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: