BlueCheeser ransomware: what it is and how to remove it
BlueCheeser ransomware is a malware string that employes the Advanced Encryption Standard to lock up all files that are located on the infected device. Afterward, all filenames receive the .himr extension and the malware starts providing ransom demands via Instructions.txt Notepad message.
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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BlueCheeser ransomware: summary
| Distribution | The malware gets distributed through stealth techniques such as email spamming, the delivery of infected attachments, cracked software, fake updates, malvertising, infectious links, etc. |
|---|---|
| Name | BlueCheeser ransomware |
| Category | Ransomware virus/malware |
| Discoverer | Raby |
| Detection list | According to VirusTotal information, this malicious string has been discovered by 44 AV engines out of the total 70, at the time of writing; no Microsoft detection name is known for this name |
| Encryption | The cyber threat employs the Advanced Encryption Standard and locks all the files and documents that are found on the targeted PC. All of the filenames get .himr extension added |
| 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 17 more facts
| Ransom demands | Cybercriminals provide ransom demands that reach up to $400 in Bitcoin. Also, they add the Bitcoin wallet number in the Instructions.txt ransom note |
|---|---|
| Target | According to the language in which the ransom note is written, the crooks are targetting English-speaking people |
| Related file | Once the malware breaks through the system's security, it can start planting on the computer whatever it wants. This includes the BlueCheeser.exe executable that is injected into the Windows Task Manager area |
| Termination | Get rid of the ransomware virus as soon as you find it lurking on your computer system. For this process, employ only reliable antimalware tools |
| Contact | Not recorded in our earlier report |
| Encrypted file extension | .himr |
| Decryptor | No free decryptor is known for this variant; check No More Ransom (nomoreransom.org) for updates |
| Ransom note | A message left on the computer; the text is quoted in full below |
| Damage | Not recorded in the old report |
| Type | File-encrypting ransomware |
| Symptoms | Files renamed with a new extension, a Windows Security "Threats found" notification and a ransom note left in folders |
| Evidence | 5 write-ups by security sites; no sample analysed yet |
| Encrypted files | .himr |
| Free decryptor | No free decryptor is known (checked 7 October 2026) |
| First seen | 7 February 2020 |
| Microsoft Defender name | Trojan:Win32/Occamy.C |
| Facts checked | 7 October 2026 |
What antivirus programs call BlueCheeser ransomware
Microsoft Defender reports BlueCheeser ransomware as Trojan:Win32/Occamy.C.
In a Defender name, the part before the colon is the category, the part after it is the platform, and the part after the slash is the family Microsoft assigned. A suffix after ! is an internal Microsoft marker, not a different threat.
Generic labels such as Agent, GenericKD or Malware.AI only say that a file looks malicious, not what it does; our guide to antivirus detection names shows how to read them.
- File extension:
.himr - Note file:
the ransom note
From our report of Feb 2020 · not reviewed since
More from our earlier report on BlueCheeser ransomware
- If you have discovered any system compromisation on your Windows machine, try using software such as for fixing the altered areas
How BlueCheeser ransomware behaves
From our report of Feb 2020 · not reviewed since
BlueCheeser ransomware - a file-encrypting parasite that urges payment of $400 in Bitcoin cryptocurrency
BlueCheeser ransomware is a malware string that employes the Advanced Encryption Standard to lock up all files that are located on the infected device.
Afterward, all filenames receive the .himr extension and the malware starts providing ransom demands via Instructions.txt Notepad message. BlueCheeser ransomware includes the crooks' Bitcoin wallet address and urges to transfer $400 in BTC. This is the total price required for the release of locked files. According to the English language that is used for writing the ransom message, hackers are targeting English-speaking people.
First discovered by a cybersecurity researcher named Raby, BlueCheeser ransomware arrives at the computer system with the help of deceptive techniques such as email spam, hacked RDPs, cracked software, fake flash player updates, malvertising, or infectious hyperlinks. After the infiltration process, the ransomware virus brings the BlueCheeser.exe file to the Windows computer system and includes the executable in the Windows Task Manager section.
According to VirusTotal provided information, BlueCheeser ransomware has been detected by 44 AV engines out of the total 70 available ones. Some of the detection names include Gen:Heur.Ransom.Imps.3, Trojan.Encoder.30952, HEUR:Trojan-Ransom.MSIL.Gen.gen, Trojan:Win32/Occamy.C, Ransom_Gen.R011C0WAC20, and others.
BlueCheeser ransomware alters the Windows Registry and Task Manager for its own purposes. The cyber infection ensures that it is booted every time when the infected computer turns on. In order to do this, the malware includes specific keys and processes to the sections that are mentioned above.
Additionally, BlueCheeser ransomware can be able to scan the entire computer system once in a while and look for encryptable documents. The malicious actors want to make sure that no components have been left unencrypted.
Afterward, BlueCheeser ransomware uses the Advanced Encryption standard to lock up files such as word documents, PDF documents, excel sheets, audio files, video files, .zip content, .exe components, and many more. Once the encryption is performed, the user cannot access the blocked files properly anymore.
However, you should expect that BlueCheeser ransomware will try to harden the recovery process for you. This can happen by deleting the Shadow Volume Copies of encrypted files and documents by running specific PowerShell commands. Also, both encryption and decryption keys are safely stored on a remote server that is reachable only for the criminals.
BlueCheeser ransomware developers try to frighten the victims by claiming that their files will be lost forever if they do not agree to pay. This type of claim is written as the last line of the Instructions.txt ransom message:
BlueCheeser virus might also target your Windows hosts file and aim to permanently damage it. This type of activity is performed when the cybercriminals want to prevent users from entering various cybersecurity forums and pages.
However, you should know that there is a big reason not to pay the cybercriminals, no matter how frightening BlueCheeser ransomware looks to you. The main fact is that hackers are very likely to scam their victims. They might provide you a fake tool or no key at all after you pay them the demanded ransom and just simply run off uncaught.
BlueCheeser ransomware makes the computer system vulnerable to other infections and might even disable the antivirus software to let in some other threats. Ransomware viruses are often used for the distribution of other malware such as trojans. These parasites aim to steal personal information and money, mine cryptocurrency, overuse the CPU power.
If you are looking for a way to avoid these possible consequences, the best thing to do would be to remove BlueCheeser ransomware from your Windows computer system and get rid of all the additional malicious products that were injected in your device during the ransomware attack.
You can successfully complete the BlueCheeser ransomware removal with the help of reliable antimalware products that will take care of the task for you. A piece of advice would be not to try to get rid of the cyber threat on your own as there is a chance of failure due to the complexity that this parasite has.
If you have any trouble with the elimination, try rebooting your PC in Safe Mode with Networking first. When BlueCheeser ransomware is permanently gone, you should start thinking about data recovery possibilities. Travel to the very end of this article where you will find three file restoring options some of which might appear really handy.
From our report of Feb 2020 · not reviewed since
Be aware of unknown email messages
Ransomware is quite commonly delivered through infectious emails that pretend to be official letters from healthcare, financial, or shipping organizations.
Such messages can travel to your email spam section but might also fall in the inbox. Regarding this fact, it is very important to measure the expectancy of such a letter.
According to NoVirus.uk experts, if you have not been waiting for a particular email message to come, you should think if its links or attached documents are worth loading. If you have already downloaded the questionable file, do not risk your computer's safety by launching the attached component without scanning it with a trustworthy antivirus program.
Furthermore, you should always check if the message is coming from an official email or some type of weird-looking one. Plus, if you find any grammar mistakes in the contact of the text message, this might be an accurate sign that you are dealing with something unknown as reliable companies would not leave any mistakes in their official texts.
To add, ransomware infections can also get distributed through other sources such as hacked RDPs that included weak passwords or none at all, fake flash player updates, malvertising ads, etc. You should always be careful while browsing the Internet and make sure to employ a reliable antivirus product.
The BlueCheeser ransomware note
Looks like all your desktop files have been encrypted!
To decrypt, send $400 to the bitcoin wallet: 43IU64UGG645G37I670IITYYR5093U55KJ5HE
RIP Your personal files if you dont pay...
How to remove BlueCheeser 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 BlueCheeser 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
BlueCheeser ransomware encrypts everything it can reach, including drives and shares you connect later. Cut the network first: cable out, or Wi-Fi off from the taskbar.
Then unplug every USB stick and backup disk and pause cloud sync, so the encrypted versions do not replace your online copies. Do not reconnect any of them until the ransomware is removed from the Windows 11 or Windows 10 PC.
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
Copy
the ransom noteand one or two files ending in.himrto a USB stick, and leave the originals where they are.From another device, upload the note and a sample file to ID Ransomware or No More Ransom's Crypto Sheriff, which name the family from the note, the extension and the file structure.
Write down the contact address and your personal ID from the note, because a decryptor or the police may ask for them.
Warning: Never contact the attackers from the infected Windows 11 or Windows 10 PC.
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
For BlueCheeser ransomware, no free decryptor is known (checked 7 October 2026). Search the family name in the No More Ransom decryption tools list and in the free decryptors of Emsisoft, Avast and Kaspersky, because new tools appear years after an attack.
Important: Keep the encrypted files even if nothing works today, and do not pay before every free option is ruled out: payment does not guarantee a working key.
Decryptors run on Windows 11 and Windows 10, but only after the ransomware itself is removed.
Full procedure with screenshots: Ransomware: first steps, finding a decryptor and recovering files
Step 4: Remove the ransomware before you restore or decrypt
Restoring or decrypting files while BlueCheeser ransomware still runs lets it encrypt them again. Run a Full scan in Windows Security > Virus & threat protection > Scan options, then the Microsoft Defender Antivirus (offline scan).
If the ransomware blocks Windows Security, start Safe Mode with Networking and scan from there. Some families install a password stealer as well, so let both scans finish on Windows 11 or 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
Open Command Prompt as administrator and run
vssadmin list shadows. If it lists copies dated before the attack, right-click a folder with encrypted files in File Explorer, choose Properties > Previous Versions, and open or restore a version from before that date.ShadowExplorer, a free tool, shows the same copies when the tab is empty or hidden. Most current families delete shadow copies, so an empty list is normal, but the check takes two minutes on Windows 11 or Windows 10.
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
Restore from an external backup, File History or OneDrive's version history, choosing a date before the attack. Connect the backup drive only after the scans are clean, or the ransomware encrypts it too.
If there is no backup, file recovery software can sometimes find the deleted originals, because some ransomware writes an encrypted copy and deletes the original file.
Stop writing to the drive and try recovery on Windows 11 or Windows 10 before new files overwrite the space.
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.
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 Feb 2020 · not reviewed since
BlueCheeser ransomware removal guidelines
BlueCheeser ransomware removal should be taken care of as soon as possible by using specific tools only.
Anti-spyware and anti-malware products are the best help in this type of situation as they can get rid of all the malicious components that the virus has planted. However, if your antivirus is having some trouble with detecting or removing the ransomware, you should try booting your computer in Safe Mode with Networking or activating System Restore.
When you remove BlueCheeser ransomware from your Windows device, it is time to search for some damage that might have been applied by the malware. Tools such as and are capable of scanning the computer system. If this software provides any results with system problems and damage, you can try repairing all the altered objects by employing another automatical utility such as .
[GI=method-1]To deactivate malicious settings and changes on your Windows computer system, you should boot your device in Safe Mode with Networking by employing the following instructions.
[GI=method-2]To disable the ransomware virus and all the malicious changes that it has brought to your device, you should opt for the System Restore feature. Enable this function with the help of the following guidelines.
If the ransomware virus has encrypted your files, you can try repairing some of them by using this piece of software and completing every step as required.
Activate Windows Previous Versions feature for data recovery.
Try using this type of software if the ransomware has affected your files. However, make sure that you have booted the System Restore feature in the past, otherwise, this method might not work.
Shadow Explorer might be helpful for file restore.
If the ransomware virus did not permanently delete or destroy your files' Shadow Volume Copies, you can give this piece of software a try.
Cybersecurity experts are still working on the official .himr files decrypter.
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 .himr 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.
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 BlueCheeser ransomware
Is there a decryptor for .himr files?
That depends on the family behind the .himr 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.
Did BlueCheeser ransomware steal my files or passwords?
We do not know yet. Nothing published so far shows data theft by BlueCheeser ransomware, but the only confirmed sign is files that end in .himr 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.
How do I open .himr files?
You cannot open them by renaming or by choosing another program. The .himr ending shows that BlueCheeser 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 BlueCheeser ransomware. Store the encrypted files on an external disk until then.
Should I pay the ransom?
We advise against it, and so do the FBI, Europol and national cyber agencies. Payment does not guarantee a working tool: some attackers never reply, some tools damage files, and some variants have no decryptor at all. Paying also funds further attacks and can make you a target again.
Before considering payment, try every recovery option in this guide and report the attack. Companies must involve their legal adviser and insurer, because payments to sanctioned groups can be illegal. If files are truly irreplaceable, store the encrypted copies and wait; decryptors sometimes appear later.
Can a data-recovery company decrypt my files for a fee?
Only if a decryptor already exists or the company pays the attackers for you. Some "ransomware recovery" services advertise that they can decrypt families with no known flaw; in practice they negotiate with the attackers and add their own fee. Others use the same free tools listed on No More Ransom.
Before you hire anyone, ask in writing how they will recover the files, whether they will contact the attackers and what happens if they fail. A legitimate service answers clearly. If a free decryptor exists for your family, you can run it yourself.
How did BlueCheeser ransomware get on my computer?
The way BlueCheeser 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 .himr 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.
Is BlueCheeser 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 the name Trojan:Win32/Occamy.C 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/Occamy.C together with the word Microsoft to find its entry in Microsoft's security encyclopedia.
Should I open the ransom note?
Reading it is fine if you open it in Notepad. A plain text the ransom note cannot harm the PC. Be careful with notes in HTA or HTML format: double-clicking those runs them in a window that can contain scripts, so right-click and choose Open with > Notepad instead.
The note tells you the contact addresses, the claimed amount and the deadline. Do not visit links or write to the addresses from this PC. Use the note to identify the family and check for a free decryptor first.
Will Fortect remove BlueCheeser 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 BlueCheeser 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: Advanced Encryption Standard (read October 7, 2026)
- Twitter: Raby. Twitter Posts (read October 7, 2026)
- Virus Total: 44 engines detected this file. BlueCheeser.exe (read October 7, 2026)
- CISA: StopRansomware (read October 7, 2026)
- No More Ransom (read October 7, 2026)