Fuerboos: what it is and how to remove it
Fuerboos trojan is a generic name used by Windows Defender's machine learning technology to describe malware that has not been encountered before. The detection can indicate the infection of ransomware, a backdoor, botnet, banking trojan, or a crypto miner.
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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Fuerboos: summary
| Name | Fuerboos |
|---|---|
| Also known as | Trojan:Win32/Fuerboos.C!cl |
| Type | Trojan, malware |
| Infiltration | Malicious executables, software cracks, spam emails, torrent sites, exploits, etc. |
| Symptoms | Varies depending on the malware type |
| Risk factors | Stolen bank account information and other sensitive details, infiltration of other malware, loss of personal files, etc. |
| 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
| Termination | Delete the infection with anti-malware software |
|---|---|
| Detection names | No Microsoft detection name is known |
| Distribution | Not recorded in the old report |
| Damage | Not recorded in the old report |
| Evidence | 5 write-ups by security sites; details still limited |
| First seen | 17 May 2019 |
| Microsoft Defender name | Trojan:Win32/Fuerboos |
| Facts checked | 6 October 2026 |
What Fuerboos does on an infected PC
From our report of May 2019 · not reviewed since
Avoid malware by being attentive online
There are many ways to get infected with malware while browsing the internet.
While many methods include users initiating the infection themselves, some, more sophisticated malware distribution methods require no user interaction at all. For example, drive-by downloads, exploit kits, software vulnerabilities, and other techniques can inject malicious code without users initiating it. However, in most cases, infections occur due to negligence from the user part.
To avoid malware infections, follow these tips from security experts:
- Install reputable anti-malware software with real-time scanning feature;
- Make sure Windows and the installed apps are patched with the latest security updates;
- Treat every email with attachments and/or hyperlinks as a potential threat - scan them with tools like Virus Total;
- Do not download/execute cracks or pirated software;
- Use ad-blockers on sites that are considered to be high-risk (porn, torrent, gambling, etc.);
- Enable two-factor authentication for your important accounts and use password managers;
- Backup your files on an external drive or a virtual storage.
From our report of May 2019 · not reviewed since
More from our earlier report on Fuerboos
- Symptoms of infection vary from threat to threat.
- In general, threat activity can result in unusual system behaviors, including unexpected opening of windows, unusual network connections identified by your firewall, and decreased system performance.
What Fuerboos can steal or download
From our report of May 2019 · not reviewed since
Fuerboos trojan is a generic name used by Windows Defender's machine learning technology to describe malware that has not been encountered before.
The detection can indicate the infection of ransomware, a backdoor, botnet, banking trojan, or a crypto miner. Depending on the type of infection, these malicious programs might have different goals, including money extortion, sensitive information harvesting, spying, proliferating another malware, etc.
Nevertheless, because Trojan:Win32/Fuerboos is a heuristic detection, it can also indicate a false positive, as it happens with similar detections, such as Win32/Heri, IDP.Generic, and many others. Users said that legitimate tools like ArangoDB , WinZip, as well as Blizzard's video game Diablo II.
While it is possible to be a false positive, it is necessary to find out whether or not the detection of Fuerboos trojan poses any threat to your computer first.
The best way to do that is by scanning your device with another anti-malware tool and even confirming with the developers of the program in question. Nevertheless, if the infection is real, it is vital to remove Fuerboos virus as soon as possible.
Fuerboos false positive is detected due to the operation patterns of certain applications. For example, many newly-created apps establish a new Windows service that tracks the incoming requests in the combination of the rare binary - the trait of the newest releases.
If Fuerboos trojan infection is not a false positive, however, you might be facing serious consequences, as threat actors might:
Unfortunately, but Trojan:Win32/Fuerboos symptoms are not consistent, as it depends on the infection type:
Fuerboos removal should only be performed if you are sure that the detection is genuine. You can use Windows Defender or other security software to terminate the malicious activity on your machine.
- steal money directly from your bank account by remotely controlling your computer;
- execute arbitrary code and upload other malware on your device;
- include you in a botnet operation;
- lock up your files and demand ransom for the decryption tool;
- steal your sensitive information and sell it on the Dark Web;
- secretly mine cryptocurrency by abusing your system resources, increasing electricity bills, slowing down the operation of the PC and deteriorating the hardware, etc.
How to check the PC for Fuerboos
If Windows Security shows Trojan:Win32/Fuerboos, it has found Fuerboos or a file that belongs to it.
Write the name down before you click Remove: it is the most useful search term later, and you will need it if you report the incident.
A family name in the label is more informative than a heuristic one. Our page on why one threat has many antivirus names lists the common formats and what each part means.
How to remove Fuerboos
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: Delete scheduled tasks that bring it back
Programs like Fuerboos add a scheduled task so they return after an uninstall or reopen a page at every sign-in. Start Task Scheduler, open Task Scheduler Library and sort by Last Run Time to see what ran recently.
On the Actions tab, a program in a user folder, a script or a web address is a warning sign; right-click such a task and choose Delete.
Tasks with names copying Google, Edge or Windows updaters but pointing to an odd folder are typical. The tool looks 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
Step 2: Remove it from startup
Press Ctrl + Shift + Esc to open Task Manager and select Startup apps (Windows 11) or the Startup tab (Windows 10). Disable entries you do not recognise, especially ones with no publisher or with a name that copies a Windows component.
Right-click an entry and choose Open file location to see where it runs from: programs in
%AppData%or%Temp%deserve a closer look. Some entries are not listed there but in the registry Run keys, which the procedure below shows how to check.Full procedure with screenshots: Stop apps from opening at startup On uGetFix
Step 3: Delete the folders left behind
Uninstalling often leaves the program's folders, and some threats reinstall themselves from them.
Press Windows + R, type
%LocalAppData%and press Enter, then do the same for%AppData%and %ProgramData%, and look for folders named after Fuerboos, its publisher or created on the day the problem started. Delete those folders, and check C:\Program Files and C:\Program Files (x86) too.If Windows says a file is in use, end it in Task Manager or delete the folder after a restart in Safe Mode. The folders are the same in Windows 11 and Windows 10.
Full procedure with screenshots: Remove what malware leaves behind in Windows
Step 4: Scan the PC, then run the offline scan
A scan finds the parts of Fuerboos that the manual steps cannot see. In Windows Security > Virus & threat protection > Scan options, start a Full scan and quarantine what it reports.
Follow it with Microsoft Defender Antivirus (offline scan) > Scan now, which restarts the PC and checks the disk while Windows and the malware are not running.
It takes about 15 minutes and works the same in Windows 11 and Windows 10. If either scan finds something, run the full scan again after removal until it comes back clean.
Windows 11: Windows Security > Virus & threat protection > Scan options. Full procedure with screenshots: Run a Microsoft Defender Offline scan
Step 5: Change passwords from another device and sign out other sessions
Fuerboos can copy saved passwords, cookies and session tokens and send them out in seconds, so cleaning the PC does not undo the theft.
Change your passwords on a device that was never infected, starting with the e-mail account, since every other reset goes through it. On each account, end all other sessions and check the recovery e-mail, phone number and forwarding rules.
Then turn on two-step verification. Sign in on the Windows 11 or Windows 10 PC again only after the offline scan is 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.
Manual removal using Safe Mode
Important! →
Manual removal guide might be too complicated for regular computer users. It requires advanced IT knowledge to be performed correctly (if vital system files are removed or damaged, it might result in full Windows compromise), and it also might take hours to complete. Therefore, we highly advise using the automatic method provided above instead.
Step 1. Access Safe Mode with Networking
Manual malware removal should be best performed in the Safe Mode environment.
Windows 7 / Vista / XP
- Click Start > Shutdown > Restart > OK.
- When your computer becomes active, start pressing F8 button (if that does not work, try F2, F12, Del, etc. - it all depends on your motherboard model) multiple times until you see the Advanced Boot Options window.
- Select Safe Mode with Networking from the list.
Windows 10 / Windows 8
- Right-click on Start button and select Settings.
- Scroll down to pick Update & Security.
- 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.
- Press Restart.
- Now press 5 or click 5) Enable Safe Mode with Networking.
Step 2. Shut down suspicious processes
Windows Task Manager is a useful tool that shows all the processes running in the background. If malware is running a process, you need to shut it down:
- Press Ctrl + Shift + Esc on your keyboard to open Windows Task Manager.
- Click on More details.
- Scroll down to Background processes section, and look for anything suspicious.
- Right-click and select Open file location.
- Go back to the process, right-click and pick End Task.
- Delete the contents of the malicious folder.
Step 3. Check program Startup
- Press Ctrl + Shift + Esc on your keyboard to open Windows Task Manager.
- Go to Startup tab.
- Right-click on the suspicious program and pick Disable.
Step 4. Delete virus files
Malware-related files can be found in various places within your computer. Here are instructions that could help you find them:
- Type in Disk Cleanup in Windows search and press Enter.
- Select the drive you want to clean (C: is your main drive by default and is likely to be the one that has malicious files in).
- Scroll through the Files to delete list and select the following:
Temporary Internet Files
Downloads
Recycle Bin
Temporary files - Pick Clean up system files.
- You can also look for other malicious files hidden in the following folders (type these entries in Windows Search and press Enter):
%AppData%
%LocalAppData%
%ProgramData%
%WinDir%
After you are finished, reboot the PC in normal mode.
From our report of May 2019 · not reviewed since
Remove Fuerboos of if it is not a false positive
Before you remove Fuerboos virus from your computer, you need to make sure that it is not a false positive.
The easiest way to do so is by downloading and installing alternative anti-malware software, such as or . All you have to do is download the security application, install it, and run a full system scan.
If any of the AV engines detect the infection as well, it is a high chance that it is not a false positive. If the virus is tampering with the anti-malware application, enter Safe Mode with Networking - we explain how below.
Nevertheless, because heuristic detection deals with brand new and never discovered threats, the best way to find out whether the program in question is malicious is by contacting its developers or flag it up on official anti-virus provider forums.
Once you are sure it is malware, you should proceed with Fuerboos removal as soon as possible to avoid such consequences as identity theft, money loss, or personal data leak.
[GI=method-1]To remove Trojan:Win32/Fuerboos safely, enter Safe Mode with Networking as explained below:
After removal: passwords, accounts and prevention
Accounts come next
Because the PC showed the Windows Security detection Trojan:Win32/Fuerboos, 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.
Do not let government spy on you
The government has many issues in regards to tracking users' data and spying on citizens, so you should take this into consideration and learn more about shady information gathering practices.
Avoid any unwanted government tracking or spying by going totally anonymous on the internet.
You can choose a different location when you go online and access any material you want without particular content restrictions. You can easily enjoy internet connection without any risks of being hacked by using VPN.
Control the information that can be accessed by government any other unwanted party and surf online without being spied on. Even if you are not involved in illegal activities or trust your selection of services, platforms, be suspicious for your own security and take precautionary measures by using the VPN service.
Backup files for the later use, in case of the malware attack
Computer users can suffer from data losses due to cyber infections or their own faulty doings.
Ransomware can encrypt and hold files hostage, while unforeseen power cuts might cause a loss of important documents. If you have proper up-to-date backups, you can easily recover after such an incident and get back to work. It is also equally important to update backups on a regular basis so that the newest information remains intact - you can set this process to be performed automatically.
When you have the previous version of every important document or project you can avoid frustration and breakdowns. It comes in handy when malware strikes out of nowhere. Use for the data restoration process.
Questions about Fuerboos
What does the name Trojan:Win32/Fuerboos 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/Fuerboos together with the word Microsoft to find its entry in Microsoft's security encyclopedia.
Can I ignore Trojan:Win32/Fuerboos 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/Fuerboos reappears, follow the removal steps in this guide.
Is Microsoft Defender enough to remove Fuerboos?
For most home PCs it is a solid first step. Defender detects this threat as Trojan:Win32/Fuerboos, and a full scan followed by an offline scan covers the places where Fuerboos usually hides. The offline scan runs before Windows starts, so malware that hides while Windows is running cannot interfere: Run a Microsoft Defender Offline scan.
Defender does not undo everything, though. It does not restore browser settings, decrypt files or change passwords that may have been copied, which is why this guide has separate steps for those. If Defender finds the same item again after removal, something else keeps reinstalling it.
How do I know if my PC has Fuerboos?
Often you do not, which is the point of a trojan. Possible signs are an antivirus alert naming Fuerboos or a generic trojan detection, unknown programs or scheduled tasks, processes with random names in Task Manager, browser extensions you did not add, security settings turned off, slower performance, or account alerts about logins from unknown places.
The reliable check is a full scan followed by Microsoft Defender's offline scan. If you recently ran a crack, a fake installer or a command a website told you to paste, scan even without symptoms.
Why can't I find Fuerboos in antivirus databases?
Because it is new or because it is listed under a different name. Antivirus companies name threats after the family they belong to, and a program that appears as Fuerboos on your PC may carry a generic or unrelated label in their databases.
Many new samples are first detected only by behaviour, without a family name. What you saw, the Windows Security detection Trojan:Win32/Fuerboos, is enough to act on:
- end the program
- remove its startup entry
- run a Microsoft Defender offline scan
- secure your accounts
A detection name from a scan is worth noting for later.
I found AnyDesk or ScreenConnect that I did not install. Is that Fuerboos?
Not necessarily Fuerboos, but it is a warning sign. These are legitimate remote support tools, and criminals use them as ready-made backdoors, especially after tech support scams or fake invoice calls.
If you did not install it and no one you trust set it up, uninstall it, change passwords from a clean device and check your bank account. If someone connected to your PC through it, follow the steps for remote access trojans and consider a Windows reset. Installed apps sorted by date shows when it appeared.
My antivirus was on. How did a trojan get past it?
Antivirus programs see a file only when it is written or run, and criminals test each new build against popular scanners before release. Detection catches up within hours or days, which is often after the first victims ran it.
Archives with passwords, installers that fetch the malware later, and scripts run through PowerShell make the job harder. That is why behaviour such as downloading cracks or pasting commands matters more than any setting. Keep Windows and Defender updated, and turn on Reputation-based protection in App & browser control.
Should I report Fuerboos?
Report it if you lost money, if accounts were taken over, if you are a business, or if the trojan came through a scam call. A police or national cybercrime report gives you a reference number for your bank and insurer and helps link cases.
You do not need to report a trojan that antivirus blocked before it ran. Before reporting, write down the dates, the detection name, file names and any messages or transactions linked to the attack; screenshots of antivirus alerts are useful evidence. The country list is in the report section above.
How dangerous is Fuerboos?
Treat it as serious until proven otherwise. The visible sign is the Windows Security detection Trojan:Win32/Fuerboos, and programs that behave this way often have more abilities than they show:
- copying passwords
- downloading other malware
- giving remote access
Its family is not known yet, so nobody can say which of these it uses. The good news is that the response is the same in every case and takes about an hour:
- cut the network
- remove the startup entry
- run an offline scan
- change passwords from a clean device
If someone had remote control, a full reset is safer.
Will Fortect remove Fuerboos?
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 Fuerboos, 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
- GotHub: Windows 10 - Installer recognized as trojan (Win32/Fuerboos.A!cl) by Defender #4170 (read October 6, 2026)
- Blizzard Entertainment: Trojan:Win32/Fuerboos.C!cl (read October 6, 2026)
- Microsoft: Trojan:Win32/Fuerboos.C!cl (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)