Trojan:Win32/Mamson!MSR: what it is and how to remove it
Trojan Mamson is an infection that can easily affect various functions of the machine once it is added to the computer. Hackers might use the threat to obtain information or even spread other threats like ransomware.
Facts checked October 6, 2026. Removal steps tested on Windows 11 (26H2) and checked against Microsoft's and the browser makers' current documentation. Sections marked as our earlier report are the original text: they describe the threat as it was then and have not been reviewed since. The 2026 status, the removal steps and the questions are current.
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Trojan:Win32/Mamson!MSR: summary
| Distribution | Files attached to spam emails can contain a malicious payload, pirating platforms, torrents deliver files with additional pieces spreading malware |
|---|---|
| Name | Trojan:Win32/Mamson!MSR |
| Type | Trojan, malware |
| Issues | The threat can silently run on the machine and cause problems with the performance, security of the PC and lead to additional infections and damage |
| Possible symptoms | The slowness of the machine, suspicious processes running in the background, other threats installed, notifications from AV programs |
| Danger | Trojans can be set to act as a vector for different malware or directly steal information or even data from the computer. This type of virus is silent and can be extremely dangerous while running unnoticed |
| Removal | Scan the PC with security software to find and remove the malware and anything installed with it. Fortect scans Windows for malware and repairs the system files and settings it damaged. Remove it nowTo use the full-featured product, you have to purchase a license for Fortect. The scan is free. |
Show 8 more facts
| Detection names | No Microsoft detection name is known |
|---|---|
| Damage | Not recorded in the old report |
| Symptoms | An unknown process in Task Manager and a Windows Security "Threats found" notification |
| Evidence | 4 write-ups by security sites; no sample analysed yet |
| File names | ReimageRepair.exe |
| First seen | 24 August 2021 |
| Microsoft Defender name | Trojan:Win32/Mamson!MSR |
| Facts checked | 6 October 2026 |
What Trojan:Win32/Mamson!MSR does on an infected PC
From our report of Aug 2021 · not reviewed since
Causes for the malware detections and how to deal with it
If you receive the detection alert about the same Trojan:MSIL/Mamson.CG!MTB intruder or the particular file that was concerning gets indicated as possibly infected - remove the detected pieces without a doubt. If there are no alerts from other tools and the only problem is notifications from one application, other issues can cause that.
These problems can be related to leftovers of malware that were active before. Corruption in system folders and other data related to functions of the machine can lead to serious issues and trigger some applications to not run properly. The infection results or affected parts can be responsible for the Trojan:Win32/Mamson detection notifications, so cleaning these issues can be very helpful.
Once a computer is infected with malware, its system is changed to operate differently. For example, an infection can alter the Windows registry database, damage vital bootup, and other sections, delete or corrupt DLL files, etc. When a system file is damaged by malware, antivirus software cannot do anything about it, leaving it just the way it is.
Consequently, users might experience performance, stability, and usability issues, to the point where a full Windows reinstallation is required.
Therefore, we highly recommend using a one-of-a-kind, patented technology of repair. Not only can it fix virus damage after the infection, but it can also remove malware that has already broken into the system thanks to several engines used by the program. Besides, the application can also fix various Windows-related issues that are not caused by malware infections, for example, Blue Screen errors, freezes, registry errors, damaged DLLs, etc.
- Download the application by clicking on the link above
- Click on the ReimageRepair.exe
- If User Account Control (UAC) shows up, select Yes
- Press Install and wait till the program finishes the installation process
- The analysis of your machine will begin immediately
- Once complete, check the results - they will be listed in the Summary
- You can now click on each of the issues and fix them manually


From our report of Aug 2021 · not reviewed since
What can go wrong when the Trojan:MSIL/Mamson.CG!MTB virus is active on the PC
Any infections that manage to find their way on the machine can be damaging because processes that the virus can run might be unnoticed for a while, so the goal of malicious actors is achieved. Trojan:Win32/Mamson!MSR is known for spreading using pirating platforms and malicious files from such services or even links to direct malware distribution pages.
It is possible to avoid such instances by staying away from any services like this. Torrent pages can deliver direct ransomware, and experts always note that anything that is not an official site of the developer or app store is not considered a reliable source.
If the trojan is set to act on its own without being the vector for other malware, functionalities can be various:
The activity of this intruder cannot be clear, so users do not know that the infection is there and needs to be terminated. Until it is too late and the machine is damaged, malware is persistent, or your data is stolen and already misused in a secondary attack or scam campaign.
You need to rely on proper anti-malware tools, security solutions to avoid these infections because frequent AV scans can help avoid full-on Trojan:Win32/Mamson virus attacks.
Keep tools like or on the machine and use them more often to check for any PUPs or more advanced threats. If the system is already affected by the malware, you might need some help with the AV detection applications, so rely on the guide below that shows you alternative methods and helpful tips for trojan removal.
- running processes;
- mining cryptocurrency;
- logging keystrokes;
- collecting other data or credentials;
- stopping particular functions;
- opening backdoors to other threats.
How Trojan:Win32/Mamson!MSR got on your PC
From our report of Aug 2021 · not reviewed since
Trojan Mamson is an infection that can easily affect various functions of the machine once it is added to the computer.
Hackers might use the threat to obtain information or even spread other threats like ransomware. It is common to use these silent infections like trojans, worms, malware as vectors for the cryptocurrency extortion-based pieces. The particular distribution way of these intruders allows developers to spread the virus around without causing any issues or symptoms on the system.
Users get this threat when pirating something. In many cases, torrent services allow cracking games, software, getting cheatcodes, and other pieces that are not legal or legitimate. Zip files, executables, and other data can contain the payload of this infection and trigger the launch of it quickly after the infiltration.
It is unfortunate, but threats like Mamson Trojan do not have many symptoms and are not causing any issues that could indicate problems with security or the infection in particular. It is more difficult to notice the infiltration because of this, but sometimes your anti-malware tool or a security application based on AV detection starts providing the alert about this intruder before you notice anything else on the machine.
These warnings and detection alerts can be false positives triggered by the software and other application compatibility issues. Most of the reports show that these different detection names are related to malware infections that can significantly affect the machine.
Different names and detection warnings can appear on the screen, and tools like Defender can indicate Trojan:MSIL/Mamson.CG!MTB and other heuristic names as possible threats. Luckily these detections also mean that the tool you use can remove the threat from your system.
It is also common to receive these alerts from the security tool as soon as you download anything from the internet. Do not panic when the alert states that there are possible issues with malware infiltration and that your computer is affected by the Trojan:Win32/Mamson virus. Notifications like this should encourage you to remove any threats from the machine as soon as possible.
You should get an additional anti-malware tool or security program like or and run the scan using the application, so you can see if there are any intruders or not.

How to check the PC for Trojan:Win32/Mamson!MSR
Which name will your scanner show?
Microsoft's name for Trojan:Win32/Mamson!MSR is Trojan:Win32/Mamson!MSR.
Defender sorts threats by category first, so the word before the colon tells you what kind of program was found, even if the family name means nothing to you.
Do not search for a removal tool by the detection name alone; fake "removal tools" use the same keywords. How the naming works is explained in our guide to antivirus detection names.
- File:
ReimageRepair.exe
How to remove Trojan:Win32/Mamson!MSR
A loader's job is to install other malware, so treat the PC as infected with more than one program until the scans are clean.
Step 1: Check where ReimageRepair.exe runs from and stop it
ReimageRepair.exeis the part you can see, and its location tells you whether it belongs there. Right-click it on the Processes page of Task Manager and choose Open file location, then right-click the file > Properties > Digital Signatures to see who signed it.An unsigned file, or one in a user folder such as
%AppData%, is the one to remove: end the task, then delete the file.Note the folder name, because the same folder usually holds its other files. This is the same in Windows 11 and Windows 10.
Full procedure with screenshots: Close a frozen app (Task Manager, Force Quit) On uGetFix
Step 2: Delete scheduled tasks that bring it back
Open Task Scheduler from the Start menu and click Task Scheduler Library. Select each task you do not recognise and read the Actions tab:
- a task that starts a file in
%AppData%or%Temp% - runs
powershellwith a long encoded line - opens a web address belongs to Trojan:Win32/Mamson!MSR or a similar program
Right-click such a task and choose Delete, and check the subfolders too. Leave tasks from Microsoft, your PC's maker and programs you use. Task Scheduler is the same in Windows 11 and Windows 10.

Windows 11: Task Scheduler Library, the task selected, the Actions tab shows the file it runs. Full procedure with screenshots: Remove what malware leaves behind in Windows
- a task that starts a file in
Step 3: Remove it from startup
Whatever Trojan:Win32/Mamson!MSR installed usually starts with Windows. Open Task Manager with Ctrl + Shift + Esc, go to Startup apps in Windows 11 or the Startup tab in Windows 10, and disable what you do not know, starting with entries that have an empty Publisher column.
Open file location on the right-click menu shows the file, which helps you decide and tells you what to delete later. Disabling is safe: if something you need stops working, switch it back on.
Full procedure with screenshots: Stop apps from opening at startup On uGetFix
Step 4: Delete the folders left behind
What the uninstaller leaves behind is usually in the user folders. Open File Explorer, switch on View > Show > Hidden items (in Windows 10 View > Hidden items), and go through
%LocalAppData%,%AppData%, %ProgramData% and the two Program Files folders.Sort by Date modified and delete folders that appeared together with the problem and belong to no program you use. Folders with random names that hold
.exe,.dll, .js or .ps1 files are the strongest sign.Full procedure with screenshots: Remove what malware leaves behind in Windows
Step 5: Scan the PC, then run the offline scan
Open Windows Security > Virus & threat protection > Scan options, run a Full scan and remove everything it finds. Then select Microsoft Defender Antivirus (offline scan) and click Scan now: the PC restarts and scans before Windows loads, which finds files that hide while Windows runs.
Save your work first, because the offline scan takes about 15 minutes. Both scans are built into Windows 11 and Windows 10, and a second scanner from another vendor is a useful extra opinion.

Windows 11: Windows Security > Virus & threat protection > Scan options. Full procedure with screenshots: Run a Microsoft Defender Offline scan
Step 6: Change passwords from another device and sign out other sessions
Assume that the passwords saved in this PC's browsers, and the accounts that were open in them, are known to the attacker. From a phone or a clean computer, change the e-mail password first, then banking, shopping, social and gaming accounts.
Use each service's option to sign out of all other sessions, because stolen cookies keep a session open even after a password change. Turn on two-step verification on each account. Wait with the infected Windows 11 or Windows 10 PC until the scans are clean.
Full procedure with screenshots: Turn on two-step verification / secure a hacked account
Instructions for each browser and system
The detailed steps for every browser and system this guide covers. Open the one you use.
Access Safe Mode to remove malware from Windows
If malware is not letting you use antivirus in normal mode, access Safe Mode and perform a full system scan from there. Safe Mode reduces the number of active processes, which may prevent some malware from interfering with security tools.
Windows 10 / Windows 11
- Right-click on Start button and select Settings.
- Select System (Windows 11) or Update & Security (Windows 10).

- On the left side of the window, pick Recovery.
- Now scroll down to find Advanced Startup section.
- Click Restart now.

- Select Troubleshoot.

- Go to Advanced options.

- Select Startup Settings.

- Click Restart.
- Press 5 or click 5) Enable Safe Mode with Networking.

Once you reach Safe Mode, launch , , or another reputable antivirus, update it with the latest definitions, and perform a full system scan to eradicate malware and all its malicious components.
After removal: passwords, accounts and prevention
Accounts come next
Because the PC showed an unfamiliar process called ReimageRepair.exe in Task Manager, a sign of a program that could read browser data, the clean-up is only half of the work.
The other half happens in your online accounts.
Change passwords from a clean device, beginning with e-mail; sign out of all sessions; check forwarding rules and recovery phone numbers; and turn on two-step verification with an authenticator app or a passkey. Ask your bank to replace cards saved in the browser.
Why the order matters and what to check in each account: secure your accounts after malware.
Protect your privacy - employ a VPN
There are several ways how to make your online time more private - you can access an incognito tab.
However, there is no secret that even in this mode, you are tracked for advertising purposes. There is a way to add an extra layer of protection and create a completely anonymous web browsing practice with the help of VPN. This software reroutes traffic through different servers, thus leaving your IP address and geolocation in disguise.
Besides, it is based on a strict no-log policy, meaning that no data will be recorded, leaked, and available for both first and third parties. The combination of a secure web browser and VPN will let you browse the Internet without a feeling of being spied or targeted by criminals.
No backups? No problem. Use a data recovery tool
If you wonder how data loss can occur, you should not look any further for answers - human errors, malware attacks, hardware failures, power cuts, natural disasters, or even simple negligence.
In some cases, lost files are extremely important, and many straight out panic when such an unfortunate course of events happen. Due to this, you should always ensure that you prepare proper data backups on a regular basis.
If you were caught by surprise and did not have any backups to restore your files from, not everything is lost. is one of the leading file recovery solutions you can find on the market - it is likely to restore even lost emails or data located on an external device.
Questions about Trojan:Win32/Mamson!MSR
What is ReimageRepair.exe and why is it running?
Every process is started by something:
- a program you installed
- a Windows service
- a scheduled task
- a startup entry
To learn why ReimageRepair.exe runs, find its file with Open file location in Task Manager, then look for an entry pointing to that file in Settings > Apps > Startup and in Task Scheduler.
Sort Installed apps by date to see what arrived when the process first appeared. Once you know the owner, you can decide whether to keep it, switch it off at startup or uninstall it completely.
What does the name Trojan:Win32/Mamson!MSR tell me?
Microsoft builds names in a fixed order:
- category
- then platform
- then family
- sometimes followed by a variant letter
- a suffix
The category is the most useful part for you. Trojan, Backdoor and PWS mean real malware that can download more, give remote access or steal passwords. PUA means unwanted software.
Ransom means ransomware. Suffixes such as !ml or !MTB mean the detection came from machine learning or behaviour analysis. Search for the family part of Trojan:Win32/Mamson!MSR together with the word Microsoft to find its entry in Microsoft's security encyclopedia.
ReimageRepair.exe keeps coming back. What should I do?
A process that returns after you end it has a restart mechanism, and that is a reason to treat ReimageRepair.exe as unwanted. Check Settings > Apps > Startup, Task Scheduler and the Services list for entries pointing to its folder, and disable them.
Look in Installed apps for anything added the same day and uninstall it. Then delete the folder and run a Microsoft Defender Offline scan, which works before Windows starts and can remove files that are locked or hidden while the system is running.
Can I ignore Trojan:Win32/Mamson!MSR if the PC works fine?
No. Many threats are built to leave the PC working normally while they steal passwords, use the processor or wait for instructions. A detection is Defender telling you it saw something malicious, and the absence of symptoms says nothing about its activity.
Check the action in Protection history: if it is anything other than Quarantined or Removed, remove it now. Then run a full scan. If the detection was a single file caught on download and does not return, you can move on; if Trojan:Win32/Mamson!MSR reappears, follow the removal steps in this guide.
Can I just delete ReimageRepair.exe?
Deleting ReimageRepair.exe by hand rarely removes Trojan:Win32/Mamson!MSR. While the trojan runs, Windows may refuse to delete the file, and if you succeed, a scheduled task, a service or a second copy may bring it back at the next restart.
The file can also be only one part of the infection: loaders and remote access tools often install other programs. Use the Microsoft Defender offline scan, which removes the file together with its startup entries before Windows loads, and then check startup items and scheduled tasks as described in the plan.
Will Windows Security detect Trojan:Win32/Mamson!MSR?
Yes, current Microsoft Defender definitions name it Trojan:Win32/Mamson!MSR. Make sure the definitions are up to date first: open Windows Security > Virus & threat protection > Protection updates and click Check for updates. Then run a full scan and the Microsoft Defender offline scan.
If the detection comes back after you remove it, look for the program, task or extension that brings it back, using the plan above. Detection removes files and startup entries, but it does not reverse changes Trojan:Win32/Mamson!MSR already made, so follow the other steps in this guide as well.
Is Trojan:Win32/Mamson!MSR a known trojan?
Not as a documented family, at least not yet. What is known is the visible sign, an unfamiliar process called ReimageRepair.exe in Task Manager, which matches a hidden program working for someone else.
New threats are often seen by victims weeks before researchers publish anything about them. Treat Trojan:Win32/Mamson!MSR as you would any trojan:
- remove what starts it
- run an offline scan
- change passwords from another device
If a scan reports a detection name, keep it; it usually reveals the family and whether it is known to download other malware. We update this guide when an analysis appears.
Can Trojan:Win32/Mamson!MSR spread to other devices on my network?
Most trojans aimed at home users stay on the PC they infected, but an attacker with remote access can look at the network, open shared folders and try passwords on other devices. Loaders sometimes deliver worms or ransomware that do spread.
Disconnect the PC while cleaning, run a full scan on other Windows PCs, change the router's admin password and the Wi-Fi password if they were saved on the infected PC, and update the router's firmware. If other PCs show the same detection, treat them as infected too.
Can a normal remote support program be a backdoor?
Yes. Tools such as AnyDesk, TeamViewer and ScreenConnect are legitimate, but whoever controls the account behind them controls the PC. Scammers install them during fake support calls, and some trojan campaigns install them silently because antivirus programs do not flag a genuine, signed product.
If you find one you did not set up, uninstall it, check Startup apps for related entries and change passwords from another device. If money or accounts were involved, call your bank and report the incident.
Will Fortect remove Trojan:Win32/Mamson!MSR?
Fortect scans Windows for malware and unwanted programs and repairs the system files and settings they change, and its free scan shows what it finds on your PC before you decide anything.
For Trojan:Win32/Mamson!MSR, follow the plan above as well: the browser steps take back permissions and settings that no scanner treats as a threat, and uninstalling the program that brought it removes the source.
Run Microsoft Defender's full scan and, if anything was found, its offline scan as a second opinion. If the symptoms are gone after the plan and both scans are clean, there is nothing more to do.
Sources
- Techtarget: 3 ransomware distribution methods popular with attackers (read October 6, 2026)
- Reddit: Does someone know official website of Xenos64? I keep getting Trojan Win32/Mamson!MSR virus (read October 6, 2026)
- ZOndervirus: Zondervirus (read October 6, 2026)
- FTC: How to recognize, remove and avoid malware (read October 6, 2026)
- Microsoft Learn: Microsoft Defender Offline (read October 6, 2026)