12Trojan.Win32.Krepper.ab: what it is and how to remove it
12Trojan.Win32.Krepper.ab is a trojan which performs various malicious tasks on your computer that may result in some serious threat to the stability of your system. It is a serious threat that secretly works in the background and displays undesirable commercial information.
Facts checked October 7, 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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Start the steps12Trojan.Win32.Krepper.ab: summary
| Detection names | No Microsoft detection name is known |
|---|---|
| Distribution | Not recorded in the old report |
| Damage | Not recorded in the old report |
| Name | 12Trojan.Win32.Krepper.ab |
| Type | Loader |
| Symptoms | An unknown program in Installed apps |
| 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 3 more facts
| Evidence | One write-up by a security site; details still limited |
|---|---|
| First seen | 26 April 2021 |
| Facts checked | 7 October 2026 |
What 12Trojan.Win32.Krepper.ab does on an infected PC
From our report of Apr 2021 · not reviewed since
WHAT IS 12TROJAN.WIN32.KREPPER.AB?
12Trojan.Win32.Krepper.ab is a trojan which performs various malicious tasks on your computer that may result in some serious threat to the stability of your system.
It is a serious threat that secretly works in the background and displays undesirable commercial information. 12Trojan.Win32.Krepper.ab shows advertisements in numerous pop-ups, web browser windows or toolbars. It can get into the system from unsafe websites. Some ad-supported applications include it as one of its components.
To begin from the most obvious one, you may soon notice constant slowdowns of your system or some programs crashing without no apparent reason. However, the problems are running deeper than it may seem at the beginning.
12Trojan.Win32.Krepper.ab trojan will be consuming a lot of your system resources and diminishing its performance. If this is not bad enough, it will gather various sensitive information about you like your ID number, bank account and other things which might be used for malicious purposes.
This program has been created by cyber criminals in a way that makes it very difficult to detect and remove it from your computer once and for all as it seems to be regenerating itself constantly. What is more, 12Trojan.Win32.Krepper.ab malware connects to the Internet without your permission and accesses websites that might be harmful and get your computer infected further.
The list goes on as 12Trojan.Win32.Krepper.ab trojan may affect the Windows Registry. It has the ability to corrupt any folder or file it targets and delete them automatically. Therefore, you may lost some really important information. It may also corrupt some hardware components like, for example, sound or display parameters.
Sharing you details with third parties without your knowledge may also be not a tempting option. Therefore, 12Trojan.Win32.Krepper.ab malware is no joke in order to get rid of this malicious application once and for all and to ensure the full protection of your system, perform a full system scan with some reputable anti-spyware tool like .
From our report of Apr 2021 · not reviewed since
HOW CAN 12TROJAN.WIN32.KREPPER.AB HIJACK MY COMPUTER?
12Trojan.Win32.Krepper.ab is inventive in its way of distribution.
There are various ways it can access your system. It favours one method frequently used by the distributors of malware and trojans in particular, namely distribution through infected email attachments. What is more, you can get it from an infected USB stick or another device.
Finally, there is another method employed called bundling. Bundling refers to stealth installation of various programs together with some free application. Therefore, the said free application works as a bait to lure users into downloading the entire bundle.
Therefore, you may download various potentially unwanted programs like browser hijackers and adware-type applications and even malware if you are not attentive enough and do not check each step of the installation process. What is more, avoid all sorts of suspicious third-party download managers.
How to remove 12Trojan.Win32.Krepper.ab
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
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 12Trojan.Win32.Krepper.ab 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 2: Remove it from startup
Whatever 12Trojan.Win32.Krepper.ab 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 3: 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 4: 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 5: 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
From our report of Apr 2021 · not reviewed since
HOW TO REMOVE 12TROJAN.WIN32.KREPPER.AB VIRUS?
As we have already established, 12Trojan.Win32.Krepper.ab virus is a dangerous and persistent application.
Therefore, you might trust its removal into the hands of some reliable anti-spyware tool ( , or ) in order to find whether your computer is safe.
After removal: passwords, accounts and prevention
Your passwords after 12Trojan.Win32.Krepper.ab
Removing 12Trojan.Win32.Krepper.ab does not undo what it may already have sent out while the PC showed 12Trojan.Win32.Krepper.ab in the list of installed apps.
Treat saved browser passwords and logged-in sessions on this PC as known to the attacker.
From another device, change the e-mail password first and end all its sessions. Then do the same for the bank, PayPal, Microsoft, Google and Apple accounts. Stolen session cookies keep working after a password change until you sign out everywhere.
Move crypto to a new wallet created on a clean device. A step-by-step order for every kind of account is in our guide to account security after an infection.
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 12Trojan.Win32.Krepper.ab
Is 12Trojan.Win32.Krepper.ab a virus?
Most programs that appear the way 12Trojan.Win32.Krepper.ab did are not viruses in the strict sense. They are potentially unwanted programs:
- real software that arrives bundled with other downloads and then shows offers
- changes browser settings
- starts with Windows
Some are harmless, some are annoying and a few carry adware. What makes it worth removing is that you did not choose it.
Uninstall it from Installed apps and check the startup list and the browsers for anything added the same day. If it refuses to uninstall or returns after a restart, treat it as more serious and run a Microsoft Defender offline scan.
How do I stop programs like 12Trojan.Win32.Krepper.ab from being installed again?
Most unwanted programs arrive through installers, so the fix is in how you install software. Download programs from their official sites or the Microsoft Store, not from download portals or ads above search results. During setup, choose Custom or Advanced installation and untick every extra offer, including browsers, toolbars and optimizers.
Decline update prompts that appear inside other programs unless you know them. In Windows Security, turn on reputation-based protection and potentially unwanted app blocking. These steps would most likely have stopped 12Trojan.Win32.Krepper.ab before it reached the app list.
What are the signs of a trojan infection?
Most trojans try to leave no visible signs, so look for side effects. Common ones:
- Windows Security turned off or unable to update
- new entries in Startup apps or Task Scheduler
- programs in Installed apps you did not install
- browser settings that changed by themselves
- unusual network activity while the PC is idle
- password-reset or login-alert e-mails you did not trigger
None of these proves an infection on its own. Together with an antivirus alert naming 12Trojan.Win32.Krepper.ab, they are a strong reason to follow the full plan.
Is a trojan infection worth reporting to the police?
If there was harm, yes. Unauthorised payments, accounts used for fraud, blackmail or a remote session during a scam call all belong in a report, and banks often ask for its reference number before they refund anything.
If antivirus caught 12Trojan.Win32.Krepper.ab before it ran and nothing was misused, there is nothing to report. Keep the evidence anyway:
- protection history
- the original download
- the dates
Businesses may also have to notify a data protection authority if personal data could have been accessed.
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.
Should I reset my PC because of 12Trojan.Win32.Krepper.ab?
Only if the signs point to deeper access. Reset when you see 12Trojan.Win32.Krepper.ab in the list of installed apps again after removal, when Windows Security cannot start or update, when remote access tools you did not install keep appearing, or when you simply cannot trust the PC any more.
Otherwise, the plan in this guide plus an offline scan is enough. If you do reset, choose Remove everything and Cloud download for a fresh copy of Windows, restore only documents and photos, and reinstall programs from their official sites. Change important passwords from the clean system afterwards.
Why didn't my antivirus stop 12Trojan.Win32.Krepper.ab?
New trojan builds are packed and changed often so that signatures do not match, and some are signed with stolen or bought certificates. Many arrive inside password-protected archives, which scanners cannot open until you extract them.
Some downloads also tell the user to turn off the antivirus "because it gives false alarms", a common line in cracked software instructions. Keep real-time protection on, never disable it for an installer, and run the offline scan whenever you suspect something slipped through.
Can 12Trojan.Win32.Krepper.ab 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.
Why can't I find 12Trojan.Win32.Krepper.ab 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 12Trojan.Win32.Krepper.ab 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, 12Trojan.Win32.Krepper.ab in the list of installed apps, 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.
Will Fortect remove 12Trojan.Win32.Krepper.ab?
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 12Trojan.Win32.Krepper.ab, 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
- FTC: How to recognize, remove and avoid malware (read October 7, 2026)
- Microsoft Learn: Microsoft Defender Offline (read October 7, 2026)
- Microsoft Learn: How Microsoft names malware (read October 7, 2026)