Aabn ransomware: what it is and how to remove it
Aabn file virus is a malicious program designed to encrypt personal files and demand ransom money in return for a decryption key. This type of ransomware is typically spread through email attachments or by downloading infected files from malicious websites.
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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Aabn ransomware: summary
| Distribution | Files with the payload of the virus can be distributed during pirating of files or via spam email attachments |
|---|---|
| Name | Aabn ransomware |
| Type | File-virus, cryptovirus |
| File extension | .aabn |
| Ransom note | _readme.txt; the text of the note is not in our records |
| Family | DJVU ransomware |
| 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 14 more facts
| Ransom amount | $490/$980 |
|---|---|
| Detection names | Microsoft: Ransom:Win32/StopCrypt.KM!MTB; Avast: PWSX-gen [Trj]; Combo Cleaner: Gen:Heur.Mint.Zard.52; Kaspersky: UDS:Trojan.Win32.Scarsi.gen; Malwarebytes: Trojan.MalPack.GS |
| Contact | support@bestyourmail.ch, datarestorehelp@airmail.cc |
| Encrypted file extension | .aabn |
| Decryptor | No free decryptor is known for this variant; check No More Ransom (nomoreransom.org) for updates |
| Damage | Not recorded in the old report |
| Symptoms | Files renamed with a new extension and a ransom note left in folders |
| Evidence | 4 write-ups by security sites; no sample analysed yet |
| Encrypted files | .aabn |
| Attacker contacts | support@bestyourmail.ch |
| Free decryptor | No free decryptor is known (checked 7 October 2026) |
| First seen | 19 September 2022 |
| Microsoft Defender name | Ransom:Win32/StopCrypt.KM!MTB |
| Facts checked | 7 October 2026 |
Which name will your scanner show?
Microsoft's name for Aabn ransomware is Ransom:Win32/StopCrypt.KM!MTB.
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 extension:
.aabn - Note file:
_readme.txt - Contact:
support@bestyourmail.ch
From our report of Sep 2022 · not reviewed since
More from our earlier report on Aabn ransomware
- Terminating the virus can be possible with the anti-malware tool because these security programs find all potentially malicious pieces on the machine
- Treat the machine with that can locate and repair all affected files
How Aabn ransomware behaves
From our report of Sep 2022 · not reviewed since
Aabn ransomware is the threat that makes previously functional files useless
Aabn file virus is a malicious program designed to encrypt personal files and demand ransom money in return for a decryption key.
This type of ransomware is typically spread through email attachments or by downloading infected files from malicious websites. Malicious macros get used for spreading virus payloads on various machines via the internet.
If your computer has been infected with this virus, do not contact the criminals and pay the ransom. Instead, try using a reputable malware removal tool to remove the virus and protect your computer from future attacks. These threats are not controlled by trustworthy people, so the Aabn ransomware virus needs to be removed.
The creators of the file virus will not give up their encryption key unless they are compensated with a payment of 490 US dollars in Bitcoin. If payment is not made within the first 72 hours, the ransom amount is increased by 50% in an attempt to convince victims that paying is their best and only option.
The attackers provide two email addresses (support@bestyourmail.ch, datarestorehelp@airmail.cc) for contact, but even if a victim wants to restore their data, negotiation is not advised as it will likely not be successful. Direct dealing with criminals is never a good idea, and experts never advise doing so.

From our report of Sep 2022 · not reviewed since
More about the threat
DJVU malware is often delivered in spam email attachments that contain packages with the virus payload hidden inside.
However, this family is more known for using keygens, cracks for games, and software that gets distributed online via pirating services. When these attachments or files are opened by unsuspecting victims, the virus is triggered and can begin to encrypt files on the victim's computer.
The _readme.txt file contains information about the ransom demand, including how much money you need to pay. However, don't fall victim to this! There have been other victims who have dealt with versions of this family, and it rarely results in the full recovery after payments.
From our report of Sep 2022 · not reviewed since
Issues with the virus family
The Aabn ransomware virus is a version of the Djvu ransomware family that releases new versions on a weekly basis.
The threat has been known since 2018. These recent improvements added to the variants released this year show that the infection cannot be decrypted, so this version and the recently spread variants cannot be recoverable.
Aabn file virus uses coding and encryption to make files unreadable without the correct key. Unlike earlier versions, this virus does not use offline ids, which means that online keys can be obtained by victims once they pay. However, it is also possible for researchers to decode the virus. This rarely happens, but it is still worth trying if you have been infected by this virus.
If your computer got infected with one of the Djvu variants, you should try using Emsisoft decryptor for Djvu/STOP. It is important to mention that this tool will not work for everyone - it only works if data was locked with an offline ID due to malware failing to communicate with its remote servers.
Even if your case meets this condition, somebody from the victims has to pay criminals, retrieve an offline key, and then share it with security researchers at Emsisoft. As a result, you might not be able to restore the encrypted files immediately.
Thus, if the decryptor says your data was locked with an offline ID but cannot be recovered currently, you should try later. You also need to upload a set of files - one encrypted and a healthy one to the company's servers before you proceed.
From here, there are three available outcomes:
- After pressing Download button, a small pop-up at the bottom, titled decrypt_STOPDjvu.exe should show up - click it.
- If User Account Control (UAC) message shows up, press Yes.
- Agree to License Terms by pressing Yes.
- After Disclaimer shows up, press OK.
- The tool should automatically populate the affected folders, although you can also do it by pressing Add folder at the bottom.
- Press Decrypt.
- "Decrypted!" will be shown under files that were decrypted successfully - they are now usable again.
- "Error: Unable to decrypt file with ID:" means that the keys for this version of the virus have not yet been retrieved, so you should try later.
- "This ID appears to be an online ID, decryption is impossible" - you are unable to decrypt files with this tool.


The Aabn ransomware note
The note is called _readme.txt.
We did not record the full text of the ransom note in our report.
How to remove Aabn ransomware
Tools you'll need
All of these are free except where noted. Download them on a clean device if the infected PC is offline.
- A USB stick: to keep the ransom note, two or three encrypted files and screenshots off the infected PC.
- Microsoft Defender Offline: built into Windows 11 and Windows 10; scans before Windows starts, so running malware cannot hide.
- Microsoft Safety Scanner: a second, portable scanner with current signatures; each download works for 10 days.
- ID Ransomware: identifies the family from the note and one encrypted file and says whether a decryptor exists.
- No More Ransom: the free decryptors from police and security companies; check it again every few months.
- Fortect (optional): scans Windows for malware and repairs the system files and settings it damaged. The free scan is in the box above.
How to remove Aabn ransomware and get your files back
Work in this order.
Disconnecting comes first, removal comes before any restore, and nothing here asks you to contact the attackers.
Step 1: Disconnect the PC and unplug backup drives
Unplug the network cable or turn off Wi-Fi, and disconnect USB drives, external disks and network shares, so Aabn ransomware cannot reach more files. Pause OneDrive, Google Drive or Dropbox sync, because synced folders upload the encrypted copies over the good ones.
Leave the PC on but offline while you read the next steps, since a restart can let the ransomware run again. This applies to Windows 11 and Windows 10 alike.

Windows 11: turn off Wi-Fi to take the PC offline. Full procedure with screenshots: Ransomware: first steps, finding a decryptor and recovering files
Step 2: Save the ransom note and confirm the family
Your files now end in
.aabnand the instructions are in_readme.txt. Save both to a USB stick, a copy of the note and two small encrypted files, before anything else.On another device, check them with ID Ransomware or Crypto Sheriff: the family name decides which decryptor, if any, can help. Keep the note's ID and contact line for your report.

Windows 11: the ransom note and encrypted files to copy for identification. Full procedure with screenshots: Ransomware: first steps, finding a decryptor and recovering files
Step 3: Check for a free decryptor
Our last check found that for Aabn ransomware, no free decryptor is known (checked 7 October 2026). Look again yourself in the No More Ransom list and the free decryptor pages of Emsisoft, Avast and Kaspersky, which add new families every year.
A decryptor needs the ransomware gone first, or it encrypts the files again. Keep at least one copy of the encrypted files on an external drive, even if no tool works yet.
Full procedure with screenshots: Ransomware: first steps, finding a decryptor and recovering files
Step 4: Remove the ransomware before you restore or decrypt
Removing Aabn ransomware does not bring the files back, but it has to come first. Start with Defender's Full scan, then the offline scan from the same Scan options page, which checks the disk before Windows loads.
If the scan cannot start, use Safe Mode with Networking. Delete the ransom notes only after you have saved a copy, because removal tools sometimes leave them behind on Windows 11 and Windows 10.

Windows 11: Windows Security > Virus & threat protection > Scan options. Full procedure with screenshots: Run a Microsoft Defender Offline scan
Step 5: Look for shadow copies of the files
Windows keeps shadow copies for restore points and backups, and some ransomware fails to delete them.
vssadmin list shadowsin an administrator Command Prompt tells you at once whether any exist.If they do, right-click the folder that held your files, open Properties > Previous Versions, select a version from before the attack, and click Open to check it before you Restore or copy the files out. Windows 11 and Windows 10 both have the tab.

Windows 11: vssadmin list shadows shows whether shadow copies exist. Full procedure with screenshots: Ransomware: first steps, finding a decryptor and recovering files
Step 6: Restore the files from a backup or recover deleted originals
A backup made before the attack is the surest way back. Connect it only once the PC is clean, then restore from File History, Windows Backup, OneDrive's Restore your OneDrive or your own external copies.
Without a backup, try file recovery: the originals that Aabn ransomware deleted may still be on the disk until something overwrites them. Install nothing new on the drive you want to recover from on the Windows 11 or Windows 10 PC.
Full procedure with screenshots: Recover deleted files (Recycle Bin, backups, OneDrive) On uGetFix
Instructions for each browser and system
The detailed steps for every browser and system this guide covers. Open the one you use.
Restore Windows "hosts" file to its original state
Some ransomware might modify Windows hosts file in order to prevent users from accessing certain websites online. For example, Djvu ransomware variants add dozens of entries containing URLs of security-related websites, such as 2-spyware.com. Each of the entries means that users will not be able to access the listed web addresses and will receive an error instead.
Here's an example of "hosts" file entries that were injected by ransomware:

In order to restore your ability to access all websites without restrictions, you should either delete the file (Windows will automatically recreate it) or remove all the malware-created entries. If you have never touched the "hosts" file before, you should simply delete it by marking it and pressing Shift + Del on your keyboard. For that, navigate to the following location:
C:\\Windows\\System32\\drivers\\etc\\

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.
Restore files using data recovery software
Since many users do not prepare proper data backups prior to being attacked by ransomware, they might often lose access to their files permanently. Paying criminals is also very risky, as they might not fulfill the promises and never send back the required decryption tool.
While this might sound terrible, not all is lost - data recovery software might be able to help you in some situations (it highly depends on the encryption algorithm used, whether ransomware managed to complete the programmed tasks, etc.). Since there are thousands of different ransomware strains, it is immediately impossible to tell whether third-party software will work for you.
Therefore, we suggest trying regardless of which ransomware attacked your computer. Before you begin, several pointers are important while dealing with this situation:
- Since the encrypted data on your computer might permanently be damaged by security or data recovery software, you should first make backups of it - use a USB flash drive or another storage.
- Only attempt to recover your files using this method after you perform a scan with anti-malware software.
Install data recovery software
- Download .
- Double-click the installer to launch it.

- Follow on-screen instructions to install the software.

- As soon as you press Finish, you can use the app.
- Select Everything or pick individual folders where you want the files to be recovered from.

- Press Next.
- At the bottom, enable Deep scan and pick which Disks you want to be scanned.

- Press Scan and wait till it is complete.

- You can now pick which folders/files to recover - don't forget you also have the option to search by the file name!
- Press Recover to retrieve your files.

Create data backups to avoid file loss in the future
From our report of Sep 2022 · not reviewed since
Removing the infection
Aabn file virus can be removed using proper tools that can perform the file-locking virus removal process.
Anti-malware tools and AV detection software can check systems and find all malicious programs or files. These detection rates of already existing samples show that tools like this can help significantly in removing the virus.
This will help to identify any related files or malware and remove them from your system. Experts recommend running a full system scan to ensure that all infections are removed and that no further damage can be done.
Once the scan is complete, you can then focus on recovering your files using alternate methods. If you add files on the machine while the threat is active still, the infection can lock added data again. Fortunately, there are a few different ways that you can go about recovering your files after the Aabn ransomware virus has been removed from your system.
Run tools like or and make sure to clear all infection files and double-check before doing anything with those affected files. One method is to try and use a backup that you may have created before the infection.

From our report of Sep 2022 · not reviewed since
Recovering the machine
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. Once a system file is damaged by malware, antivirus software is not capable of doing 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 reinstall is required.
Not only can it fix virus damage after the infection, but it is also capable of removing malware that has already broken into the system thanks to several engines used by the program. Besides, the application is also capable of fixing 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


Report it and recover your files
Report it
Report the attack even if you do not expect the files back: insurers and banks ask for the report number, and police use the contacts in the note to link cases.
- United States
- FBI IC3 · FTC ReportFraud
- United Kingdom
- Report Fraud (formerly Action Fraud) · NCSC
- Australia
- ReportCyber (ASD)
- EU countries
- Europol: national reporting sites
Give the victim ID, the note and the date the files were encrypted. A business that holds personal data may also have to notify its data protection authority, in the EU within 72 hours.
Protect the files you restore
Restore only after the scans are clean and the PC no longer shows files that end in .aabn and no longer open; otherwise the restored copies can be damaged again.
Then build a backup that survives the next infection:
- one copy in the cloud with version history
- one on an external drive that is disconnected between backups
- the working copy on the PC
Version history matters because a backup that syncs damaged files overwrites the good ones.
How to do this with the tools built into Windows: the 3-2-1 backup rule on Windows.
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 Aabn ransomware
Is there a decryptor for .aabn files?
That depends on the family behind the .aabn extension, which this guide cannot confirm yet from the reports alone. Check No More Ransom and ID Ransomware with your ransom note and one encrypted file; they list families with free tools.
If none exists today, keep the encrypted files and a copy of the note on a separate drive, because decryptors are sometimes published months later after flaws are found or servers are seized. Never buy a decryptor from a website that is not the security company that made it.
Should I pay the ransom in _readme.txt?
Not before you have tried everything else. Identify the family from _readme.txt and one encrypted file, check No More Ransom for a free decryptor, and look for clean copies in OneDrive, backups and Previous Versions.
Paying funds further attacks, may be illegal if the group is sanctioned, and is no promise of a working key: many victims get partial or broken decryption. If you consider paying for business-critical data, involve the police and a professional incident responder first, and never pay through intermediaries who promise their own decryption.
How do I open .aabn files?
You cannot open them by renaming or by choosing another program. The .aabn ending shows that Aabn ransomware encrypted the content, and only the matching key can reverse it. Renaming a file back to .docx or .jpg changes nothing except the icon, and it can confuse a future decryptor, so leave the names as they are.
To get the content back, use a backup, an unencrypted copy elsewhere, or a decryptor listed on No More Ransom if one exists for Aabn ransomware. Store the encrypted files on an external disk until then.
Are ransomware recovery services legitimate?
Some are, but read the offer carefully. Genuine data-recovery firms recover deleted originals from disks or rebuild damaged files, and they say so. Others promise to "decrypt any ransomware" for a fixed price, which is impossible without the key; they quietly pay the attackers and keep a margin, sometimes without telling the victim.
Be especially careful with services that contact you after you post about the attack online. Ask for references, a written method and a no-result-no-fee clause, and check the free tools on No More Ransom first.
How did Aabn ransomware get on my computer?
The way Aabn ransomware spreads has not been documented yet, so look at your own recent activity. On home PCs, ransomware most often comes with cracked programs, game cheats, key generators and fake updates, or with an e-mail attachment that was opened. On business networks, attackers usually log in through Remote Desktop with a stolen or guessed password.
Think back to what was downloaded or installed in the days before files that end in .aabn and no longer open, and check the Downloads folder and Installed apps sorted by date. Keep anything suspicious for your report, but do not run it again.
Did Aabn ransomware steal my files or passwords?
We do not know yet. Nothing published so far shows data theft by Aabn ransomware, but the only confirmed sign is files that end in .aabn and no longer open, which says nothing about what happened before. Many current ransomware attacks copy files or run a password stealer first, so it is wise to act as if they did.
From a clean device, change the passwords that were saved in the browsers on this PC, starting with e-mail and banking, sign out of all sessions and turn on two-step verification. Watch bank statements and account activity for the next few weeks.
Is Aabn ransomware the same as other ransomware with a similar name?
Not necessarily. Ransomware names come from the file extension, the note or a word in the code, so unrelated families often end up with similar names, and one family can appear under several names. The difference matters: a decryptor or advice for one family does not fit another and can damage files.
Compare the ending added to your files and the exact name of the note with the summary table at the top of this guide, then upload the note and one encrypted file to ID Ransomware from a clean device. If the result names another family, follow the guide for that family instead.
What does _readme.txt tell me about the ransomware?
Quite a lot. The file name _readme.txt, the wording, the contact addresses and the format of the personal ID are typical for each family. Uploading the note together with one encrypted file to ID Ransomware or No More Ransom's Crypto Sheriff usually names the family within seconds.
That name decides your options: some families have free decryptors, some can be partially recovered, and some cannot be decrypted at all. The note's claims about stolen data should be taken seriously but not at face value.
My files got .aabn overnight. What happened?
Ransomware often runs at night or when the PC is idle, so the encryption finishes before anyone notices. It usually entered earlier through a cracked program, a fake installer, an e-mail attachment or remote desktop with a weak password.
The .aabn extension marks every file it reached. Start by disconnecting the PC from the network, then identify the family from the ransom note and one encrypted file, check for a decryptor, and look for copies in backups and OneDrive before you consider anything else.
Will Fortect remove Aabn ransomware?
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 Aabn ransomware, 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
- Wikipedia: Macro virus (read October 7, 2026)
- ZOndervirus: Zondervirus (read October 7, 2026)
- VirusTotal: Virus detection rates (read October 7, 2026)
- VirusTotal: analysis of a Aabn ransomware sample (read October 7, 2026)
- CISA: StopRansomware (read October 7, 2026)
