Rungbu.b: what it is and how to remove it
Rungbu.b is a virus that replaces Microsoft Word documents with copies of itself. Upon infiltration, it does not delete the original file that it is about to infect but rather hides its presence on the device.
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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Rungbu.b: summary
| Distribution | Malicious spam emails, removable drives, malicious websites, etc. |
|---|---|
| Name | Rungbu.b |
| Type | Virus |
| Dangers | Damage to personal and system files |
| Detection names | No Microsoft detection name is known |
| Damage | Not recorded in the old report |
| 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 5 more facts
| Symptoms | An unknown process in Task Manager |
|---|---|
| Evidence | One write-up by a security site; details still limited |
| File names | CTFMON.EXE |
| First seen | 3 May 2021 |
| Facts checked | 7 October 2026 |
What Rungbu.b does on an infected PC
From our report of May 2021 · not reviewed since
Rungbu.b is a Visual Basic-based virus that infects MS Office documents
Rungbu.b is a virus that replaces Microsoft Word documents with copies of itself.
Upon infiltration, it does not delete the original file that it is about to infect but rather hides its presence on the device. Also, it changes the extension of such a file to .SCR and uses Microsoft Word icon to increase obfuscation.
The virus can spread in a few ways, for example, via the contaminated MS Word or other Office documents attached to a malicious email. Alternatively, users might also infect their devices after accessing a suspicious website and clicking on a malicious link.
Once installed, the parasite copies itself and attaches to various locations of Windows folders. It uses the following names for the placed files:
It is important to note that these names are commonly used by Windows and initially are not malicious. However, malware often uses the names of common system or application files in order to disguise its presence on the computer. Luckily, this trick does not work for most modern security applications, and the virus would be detected upon executing malicious actions.
As soon as the malicious files are placed, Rungbu.b will start infecting all the .DOC files as soon as they are opened. This way, the virus spreads even further. Also, it drops "desktop.ini" and "flu burung.txt" files on the system. The text file reads the following:
- CTFMON.EXE
- SPOOLSV.EXE
- SVCHOST.EXE
- SMSS.EXE
From our report of May 2021 · not reviewed since
More from our earlier report on Rungbu.b
- Perform a full system scan with powerful antivirus software
- ======= FLU BURUNG ======= Bugs Bunny say "What's up doc?"
- Duffy Duck say "I'm infected doc" So at the end of story they save the screen.
How to check the PC for Rungbu.b
- File:
CTFMON.EXE
How to remove Rungbu.b
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 CTFMON.EXE runs from and stop it
CTFMON.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 Rungbu.b 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 Rungbu.b 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.
Uninstall from Windows
Uninstall from Windows 10/8:
- Type Control Panel into the Windows search box and open the result.
- Under Programs, select Uninstall a program.
Uninstall from Windows 7/XP:
- Click on Windows Start > Control Panel (Windows XP users should click on Add/Remove Programs).
- In Control Panel, select Programs > Uninstall a program.
Remove the unwanted program:
- In the Programs and Features window, look for any recently installed suspicious entries, select them, and click Uninstall.
- If User Account Control appears, click Yes to confirm, then complete the removal.
Remove from Google Chrome
Delete malicious extensions from Google Chrome:
- Open Google Chrome, click on the Menu (three vertical dots at the top-right corner) and select More tools > Extensions.
- In the newly opened window, you will see all the installed extensions. Uninstall all suspicious extensions related to the unwanted program by clicking Remove.
Clear cache and web data from Chrome:
- Click on Menu and pick Settings.
- Under Privacy and security, select Clear browsing data.
- Select Browsing history, Cookies and other site data, as well as Cached images and files.
- Click Clear data.
Change your homepage:
- Click menu and choose Settings.
- Look for a suspicious site in the On startup section.
- Click on Open a specific or set of pages and click on three dots to find the Remove option.
Reset Google Chrome:
If the previous methods did not help you, reset Google Chrome to eliminate all the unwanted components:
- Click on Menu and select Settings.
- In the Settings, scroll down and click Advanced.
- Scroll down and locate Reset and clean up section.
- Now click Restore settings to their original defaults.
- Confirm with Reset settings.
Remove from Microsoft Edge
Delete unwanted extensions from MS Edge:
- Select Menu (three horizontal dots at the top-right of the browser window) and pick Extensions.
- From the list, pick the extension and click on the Gear icon.
- Click Remove.
Clear cookies and other browser data:
- Click on the Menu (three horizontal dots at the top-right of the browser window) and select Settings > Privacy, search, and services..
- Under Clear browsing data, pick Choose what to clear.
- Select Cookies and other site data and Cached images and files. (apart from passwords, although you might want to include Media licenses as well, if applicable) and click on Clear.
Restore new tab and homepage settings:
- Click the menu icon and choose Settings.
- Then find On startup section.
- Click Remove next to any suspicious startup page.
Reset MS Edge if the above steps did not work:
- Press on Ctrl + Shift + Esc to open Task Manager.
- Click on More details arrow at the bottom of the window.
- Select Details tab.
- Now scroll down and locate every entry with Microsoft Edge name in it. Right-click on each of them and select End Task to stop MS Edge from running.
Delete extensions from MS Edge (Chromium):
- Open Edge and click select Settings > Extensions.
- Delete unwanted extensions by clicking Remove.
Clear cache and site data:
- Click on Menu and go to Settings.
- Select Privacy, search and services.
- Under Clear browsing data, pick Choose what to clear.
- Under Time range, pick All time.
- Select Clear now.
Reset Chromium-based MS Edge:
- Click on Menu and select Settings.
- On the left side, pick Reset settings.
- Select Restore settings to their default values.
- Confirm with Reset.
- This will disable extensions and reset startup pages but will not delete bookmarks, saved passwords, or browsing history.
Remove from Mozilla Firefox (FF)
Remove dangerous extensions:
- Open Mozilla Firefox browser and click on the Menu (three horizontal lines at the top-right of the window).
- Select Add-ons.
- In here, select the unwanted extension and click Remove.
Reset the homepage:
- Click three horizontal lines at the top right corner to open the menu.
- Choose Settings.
- Under Home, set your preferred homepage and new tab settings.
Clear cookies and site data:
- Click Menu and pick Settings.
- Go to Privacy & Security section.
- Scroll down to locate Cookies and Site Data.
- Click on Clear Data...
- Select Cookies and Site Data and Temporary cached files and pages, then click Clear.
Reset Mozilla Firefox
If clearing the browser as explained above did not help, reset Mozilla Firefox:
- Open Mozilla Firefox browser and click the Menu.
- Go to Help and then choose Troubleshooting Information.
- Under Give Firefox a tune up section, click on Refresh Firefox...
- Once the pop-up shows up, confirm the action by pressing on Refresh Firefox.
Delete from Safari
Remove dangerous extensions:
- Open Safari, click Safari in the menu at the top-left of the screen, and select Preferences.
- Go to the Extensions tab, look for any suspicious entries, and click Uninstall to remove them.
Clear history and website data:
- Click Safari in the menu and pick Clear History.
- Set Clear to all history and confirm with Clear History.
Reset Safari:
- Click Safari in the menu and select Preferences > Advanced.
- Enable Show Develop menu in menu bar.
- From the menu bar, click Develop and select Empty Caches.
Delete from macOS
Remove the unwanted application:
- From the menu bar, select Go > Applications.
- In the Applications folder, look for any suspicious entries, then drag them to Trash (or right-click and pick Move to Trash).
Delete leftover files and folders:
- Select Go > Go to Folder.
- Enter /Library/Application Support and remove any suspicious folders related to the unwanted program.
- Repeat the same check in the /Library/LaunchAgents and /Library/LaunchDaemons folders, deleting any suspicious entries.
- Finally, empty the Trash to permanently remove the leftovers.
From our report of May 2021 · not reviewed since
Removal options
While it is possible to remove Rungbu.b manually, it is definitely not recommended.
Viruses can spread automatically and infect some system files in the process. This allows them resurface if the process of elimination is not performed correctly.
Therefore, we highly recommend you avoid manual removal at all costs. Instead, you should perform a full system scan with a security tool (just make sure that it has the latest updates for the malware definitions). This way, you will ensure that all virus files are deleted automatically and no other infections are present on the device.
After removal: passwords, accounts and prevention
Secure your accounts after the clean-up
Assume that whatever was saved in the browsers on this PC while the PC showed an unfamiliar process called CTFMON.EXE in Task Manager has been copied:
- passwords
- cookies
- autofill data
Work from a clean device, or from this PC once the offline scan finds nothing.
Start with your main e-mail account, because it can reset everything else, then banking and payment, then social and gaming accounts. Change each password, sign out of all sessions and turn on two-step verification: Turn on two-step verification / secure a hacked account.
The full order, including crypto wallets and card replacement, is in securing your accounts after malware.
Access your website securely from any location
When you work on the domain, site, blog, or different project that requires constant management, content creation, or coding, you may need to connect to the server and content management service more often. The best solution for creating a tighter network could be a dedicated/fixed IP address.
If you make your IP address static and set to your device, you can connect to the CMS from any location and do not create any additional issues for the server or network manager that needs to monitor connections and activities. VPN software providers like can help you with such settings and offer the option to control the online reputation and manage projects easily from any part of the world.
Recover files after data-affecting malware attacks
While much of the data can be accidentally deleted due to various reasons, malware is one of the main culprits that can cause loss of pictures, documents, videos, and other important files.
More serious malware infections lead to significant data loss when your documents, system files, and images get encrypted. In particular, ransomware is is a type of malware that focuses on such functions, so your files become useless without an ability to access them.
Even though there is little to no possibility to recover after file-locking threats, some applications have features for data recovery in the system. In some cases, can also help to recover at least some portion of your data after data-locking virus infection or general cyber infection.
Questions about Rungbu.b
What is CTFMON.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 CTFMON.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.
Can I end CTFMON.EXE in Task Manager?
Ending an unknown process is safe in the sense that Windows will warn you before you close anything critical, and a restart brings back whatever Windows needs. Ending CTFMON.EXE will not remove it, though: if a task or startup entry launches it, it returns at the next sign-in.
Use ending the process as a test. If something important stops working, it belonged to a program you use. If nothing changes and it comes back by itself, find and disable its starter, delete the file and scan the PC.
Can I just delete CTFMON.EXE?
Deleting CTFMON.EXE by hand rarely removes Rungbu.b. 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.
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 Rungbu.b 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.
Why didn't my antivirus stop Rungbu.b?
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 I keep using the PC while Rungbu.b is on it?
Not for anything that matters. As long as the program behind an unfamiliar process called CTFMON.EXE in Task Manager runs, it can see what you type and what the browser stores, and it may download more malware. Disconnect the PC from the internet while you remove it, and do your banking, e-mail and password changes from another device.
Once the offline scan finds nothing and the sign does not return after a few restarts, normal use is fine. If the scan keeps finding new items, or you cannot remove the startup entry, a reset of Windows is the safer choice.
Why can't I find Rungbu.b 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 Rungbu.b 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, an unfamiliar process called CTFMON.EXE in Task Manager, 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.
Should I reset my PC because of Rungbu.b?
Only if the signs point to deeper access. Reset when you see an unfamiliar process called CTFMON.EXE in Task Manager 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.
Can Rungbu.b 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.
Will Fortect remove Rungbu.b?
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 Rungbu.b, 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)