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Microsoft Security

MSRT April release features Bedep detection

  • Microsoft Defender Security Research Team

As part of our ongoing effort to provide better malware protection, the Microsoft Malicious Software Removal Tool (MSRT) release this April will include detections for:

In this blog, we’ll focus on the Bedep family of trojans.


The bothersome Bedep

Win32/Bedep was first detected in November 25, 2014 as a malware family made up of DLLs which has been distributed by Angler Exploit Kit. Microsoft detects Angler as:

JS/Axpergle and HTML/Axpergle have been known to carry and drop Bedep around by redirecting unsuspecting users to compromised websites.

Bedep is bothersome not only because it is carried around by an exploit kit, but because it also connects to a remote server to do the nasty:

All of the above malware families have these in common: they steal your personal information and send them to the hacker, watch what you do online, drops other malware onto your PC, and update them too.

  • Collect information about your PC to send it off to the malware perpetrator
  • Update the downloaded malware

The good thing is, Windows Defender detects and removes Bedep and its variants.

This threat has been prevalent in North America, and various parts of Latin America, Europe, and Southeast Asia.


Figure 1: The map shows Win32/Bedep’s prevalence in North America, Latin America, Europe, and South East Asia in the last six months.



Figure 2: The pie chart shows the Bedep distribution among the top 10 countries for the past six months


The exploit shellcode sometimes loads Bedep directly in the memory from the Angler Exploit Kit, without being written to disk. However, it gets written to disk at other times.

It can either be installed as 32bit DLL (Backdoor:Win32/Bedep.A) or 64bit DLL (Backdoor:Win64/Bedep.A), depending on the affected Windows OS version.

This threat is initially loaded by shellcode running in an exploited browser process (for example, iexplore.exe). Then, the threat downloads a copy of itself and injects that into explorer.exe.

We have observed that the first exploit is not enough. The attacker needs more exploits to bypass the OS or browser’s layered defenses. As a precaution, you should always be careful on clicking the User Account Control (UAC) prompts.

We’ve also seen that Bedep can drop itself as %ProgramData%\<{CLSID}>\<filename>.dll

Example path and file names: C:\ProgramData\{9A88E103-A20A-4EA5-8636-C73B709A5BF8}\acledit.dll.

It then creates the following registry entries:

In subkey: HKEY_CURRENT_USER\CLSID\%Random CLSID%\InprocServer32

Example: HKEY_CURRENT_USER\CLSID\{F6BF8414-962C-40FE-90F1-B80A7E72DB9A}\InprocServer32

Sets value: “ThreadingModel

With data: “Apartment

Sets value: “”

With data: %Bedep Filename%

Example: “C:\ProgramData\{9A88E103-A20A-4EA5-8636-C73B709A5BF8}\acledit.dll

In subkey: HKEY_CURRENT_USER\Drive\ShellEx\FolderExtensions\%Random CLSID%

Example: HKEY_CURRENT_USER\Drive\ShellEx\FolderExtensions\{F6BF8414-962C-40FE-90F1-B80A7E72DB9A}

Sets value: “DriveMask

With data: dword:ffffffff


For details about various Bedep variants, see the following malware encyclopedia entries:


Mitigation and prevention

To help stay protected from Bedep and other threats, use an up-to-date Windows Defender for Windows 10 as your antimalware scanner, and ensure that MAPS has been enabled.

Though trojans have been a permanent fixture in the malware ecosystem, there’s still something that you or your administrators can proactively do:


Jonathan San Jose


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