KCBU ransomware aims to lock your files by encrypting them
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KCBU ransomware is a new computer virus variant recently released by the STOP/DJVU ransomware gang. After being launched, this piece of malware begins encrypting every file and marks each one with an additional .kcbu extension. Once files are encrypted, the victim can no longer access them, no matter what program is used. To illustrate the procedure, see this example: 1.jpg becomes 1.jpg.kcbu, 2.docx becomes 2.docx.kcbu and so on. To make matters worse, this ransomware usually comes in tandem with information-stealing Trojans that transmit sensitive information to cybercriminals.
The aim of this ransomware is to take user’s data hostage, then demand a ransom for its release. The virus creates a text note called _readme.txt (widely known as a ransom note) for the user with instructions from the ransomware operators.
The ransom note introduces decryption tool pricing
The _readme.txt file contains a short message from the ransomware operators. They explain that data on the computer was encrypted, and in order to restore it, they demand “purchasing” a KCBU file decryption tool from them. They also explain that whoever contacts the attackers within 72 hours starting from the infection timestamp, gets a 50% discount on the decryption tools, which means the price would be $490. Otherwise, the victim has to pay the full amount, which is $980.
At the end of the ransom note, two email addresses are provided: support@fishmail.top and datarestorehelp@airmail.cc. The note recommends using them to contact the cybercriminals. In addition, there is a suggestion to test the decryption service on one file. The victim can attach one small encrypted file and send it to ransomware operators to find out whether they can actually restore the data.
Even if they can, law enforcement agencies like FBI do not recommend paying the ransom. It only encourages the criminals to continue their activities, plus, they might attempt to target you again in the future.
What is not mentioned in the ransom note is the malware that came along the data-encrypting threat. Most of STOP/DJVU ransomware versions are spread together with AZORULT, VIDAR or RedLine Stealers, all being highly malicious Trojans used for theft of sensitive information.
In order to prevent further damage, we recommend victims to remove KCBU ransomware as soon as it is possible. Boot your computer in Safe Mode with Networking and run a trustworthy AV solution, like the one we recommend (INTEGO Antivirus). It scores excellent rates in malware detection tests and provides real-time protection 24/7. As an additional step, you may want to download RESTORO, a tool that can repair virus damage caused on Windows OS files.
Ransomware Summary
| Name | KCBU Ransomware Virus |
| Type | Ransomware; Crypto-malware; Virtual Extortion Virus |
| Family | STOP/DJVU |
| Encryption type | RSA 2048 + Salsa20 |
| Previous versions | MANW, MZOP, MZQW, ERQW, EROP, ASSM, MZTU (find full list here) |
| Version | 608th |
| Extension | .kcbu |
| Cybercriminal emails | support@fishmail.top and datarestorehelp@airmail.cc |
| Additional malware dropped | Azorult or Vidar Trojan |
| Damage | The ransomware uses encryption to maliciously modify all files on the PC and marks their original names with .kcbu extension. Ransom notes called as _readme.txt will be dropped in every computer folder. This piece of malware usually drags VIDAR Stealer alongside it and also eliminates VSS from the system. On top of that, it tends to modify Windows HOSTS file to restrict computer user’s access to cybersecurity-related websites online. |
| Ransom note | _readme.txt |
| Ransom demand | $490-$980 in Bitcoin |
| Distribution | Victims often download this ransomware along illegal torrent downloads, cracked software, activators, key generators or tools like KMSPico. |
| Known software cracks to contain this malware | Corel Draw, Tenorshare 4ukey, Adobe Photoshop, Cubase, Adobe Illustrator, Internet Download Manager, Tally, League of Legends. |
| Detection names | Trojan:Win32/Azorult.FW!MTB (Microsoft), Gen:Heur.Mint.Zard.52 (B) (Emsisoft), HEUR:Trojan.Win32.Scarsi.gen (Kaspersky), Gen:Heur.Mint.Zard.52 (BitDefender), Trojan.MalPack.GS (Malwarebytes), ML.Attribute.HighConfidence (Symantec) see all detection name variations on VirusTotal |
| Removal | Remove ransomware and related malware from your PC using trustworthy software like INTEGO Antivirus. To repair virus damage on Windows OS files, download and try RESTORO (secure download link). |
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How ransomware-type malware is distributed?
STOP/DJVU ransomware variants, just like other data-encrypting and similar computer viruses, are mainly delivered in disguise of pirated/cracked software versions, fake software updates or malicious email attachments. Our research shows that KCBU virus mainly spreads via deceptive software crack websites.
Cybercriminals typically upload fake downloads to various torrent listings or websites claiming to be providers of various cracked software versions. You can read more about such deceptive sites providing dangerous downloads here. Typically, the promoted file is a password-protected archive that contains a setup.exe file. Unfortunately, upon launching it, the user receives a notification that the installer has stopped working. In the meantime, the malware begins preparations for a severe computer attack.
It is never a good idea to look for illegal software copies, even if you’re trying to save money. To avoid cybersecurity risks, ensure you download software from trustworthy and official websites only. The software provider and affiliates often provide various discounts that users can use and save money. Trying to completely bypass software license fees can result in a severe computer infection, which will lead to much higher expenses in regards of lost time and data.
Another common method used for malware distribution is email spam. The threat actors usually contact the potential targets and send some email attachments that, once opened, can lead to a computer infection. A typical trick that cybercriminals use is impersonating various companies and their representatives, claiming there is an urgent matter that needs to be taken care of. For example, the malicious email might state there is an invoice for you, or an order on its way, or claim that your subscription for an unknown service has been renewed.
The aim is to trigger user’s reaction and force him/her to open the malicious attachment or included link quickly. That being said, you should always check for suspicious signs in the email and verify if it was sent from a reliable source. For example, try to check the sender’s email address, the greeting line, overall design of the email message, and grammar mistakes. If you can spot some suspicious signs, do not open the attachments or URLs included in the message. It can lead to a severe computer infection.
Another trick used for malware distribution is deceptive software update installers advertised online. If you ever come across an aggressive pop-up ad that claims you need to update Flash or Java urgently, do not do as instructed – instead, visit the official website of the advertised software and check for updates there. If you interact with such ads without checking their reliability, you may end up installing a bunch of spyware/malware along the alleged “update.”
Remove KCBU ransomware virus and decrypt your files
If the described malware has already infiltrated your computer system, we strongly advise you to remove KCBU ransomware remains as well as other malware that may have infected the system. The guide provided below explains how to initiate the removal safely. If you do not have an AV solution yet, consider using INTEGO Antivirus. You can read more about its effectiveness in a full review on our site.
Once the malware is removed, consider scanning your computer with RESTORO to identify damage to Windows OS files and repair it wherever possible. In addition, we recommend that you change all the account passwords that you’ve used on the compromised computer.
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Our team recommends a two-step rescue plan to remove ransomware and other remaining malware from your computer, plus repair caused virus damage to the system:
STEP 1. REMOVE AUTOMATICALLY WITH ROBUST ANTIVIRUS
STEP 2. REPAIR VIRUS DAMAGE TO YOUR COMPUTER
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KCBU Ransomware Virus Removal Guidelines
Method 1. Enter Safe Mode with Networking
Step 1. Start Windows in Safe Mode with Networking
Before you try to remove KCBU Ransomware Virus virus, you must start your computer in Safe Mode with Networking. Below, we provide the easiest ways to boot PC in the said mode, but you can find additional ones in this in-depth tutorial on our website – How to Start Windows in Safe Mode. Also, if you prefer a video version of the tutorial, check our guide How to Start Windows in Safe Mode on Youtube.
Instructions for Windows XP/Vista/7 users
- First of all, turn off your PC. Then press the Power button to start it again and instantly start pressing F8 button on your keyboard repeatedly in 1-second intervals. This launches the Advanced Boot Options menu.
- Use arrow keys on the keyboard to navigate down to Safe Mode with Networking option and press Enter.
Instructions for Windows 8/8.1/10/11 users
- Open Windows Start menu, then press down the Power button. On your keyboard, press down and hold the Shift key, and then select Restart option.
- This will take you to Windows Troubleshoot screen. Choose Troubleshoot > Advanced Options > Startup Settings > Restart. Tip: If you can't find Startup Settings, click See more recovery options.
- In Startup Settings, press the right key between F1-F9 to enter Safe Mode with Networking. In this case, it is the F5 key.
Step 2. Remove files associated with the virus
Now, you can search for and remove KCBU Ransomware Virus files. It is very hard to identify files and registry keys that belong to the ransomware virus, Besides, malware creators tend to rename and change them repeatedly. Therefore, the easiest way to uninstall such type of a computer virus is to use a reliable security program such as INTEGO Antivirus. For virus damage repair, consider using RESTORO.
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Method 2. Use System Restore
In order to use System Restore, you must have a system restore point, created either manually or automatically.
Step 1. Boot Windows in Safe Mode with Command Prompt
Instructions for Windows XP/Vista/7 users
- Shut down your PC. Start it again by pressing the Power button and instantly start pressing F8 button on your keyboard repeatedly in 1-second intervals. You will see Advanced Boot Options menu.
- Using arrow keys on the keyboard, navigate down to Safe Mode with Command Prompt option and press Enter.
Instructions for Windows 8/8.1/10/11 users
- Launch Windows Start menu, then click the Power button. On your keyboard, press down and hold the Shift key, and then choose Restart option with the mouse cursor.
- This will take you to Windows Troubleshoot screen. Choose Troubleshoot > Advanced Options > Startup Settings > Restart. Tip: If you can't find Startup Settings, click See more recovery options.
- In Startup Settings, press the right key between F1-F9 to enter Safe Mode with Command Prompt. In this case, press F6 key.
Step 2. Start System Restore process
- Wait until system loads and command prompt shows up.
- Type cd restore and press Enter, then type rstrui.exe and press Enter. Or you can just type %systemroot%system32restorerstrui.exe in command prompt and hit Enter.
- This launches System Restore window. Click Next and then choose a System Restore point created in the past. Choose one that was created before ransomware infection.
- Click Yes to begin the system restoration process.
After restoring the system, we recommend scanning the system with antivirus or anti-malware software. In most cases, there won't be any malware remains, but it never hurts to double-check. In addition, we highly recommend checking ransomware prevention guidelines provided by our experts in order to protect your PC against similar viruses in the future.
Alternative software recommendations
Malwarebytes Anti-Malware
Removing spyware and malware is one step towards cybersecurity. To protect yourself against ever-evolving threats, we strongly recommend purchasing a Premium version of Malwarebytes Anti-Malware, which provides security based on artificial intelligence and machine learning. Includes ransomware protection. See pricing options and protect yourself now.
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Decrypt KCBU files
Fix and open large KCBU files easily:
It is reported that STOP/DJVU ransomware versions encrypt only the beginning 150 KB of each file to ensure that the virus manages to affect all files on the system. In some cases, the malicious program might skip some files at all. That said, we recommend testing this method on several big (>1GB) files first.
- Create a copy of encrypted file to a separate folder using Copy > Paste commands.
- Now, right-click the created copy and choose Rename. Select the KCBU extension and delete it. Press Enter to save changes.
- In the prompt asking whether you want to make the changes as file might become unusable, click OK.
- Try opening the file.
STOP/DJVU decryption tool usage guide
STOP/DJVU ransomware versions are grouped into old and new variants. KCBU Ransomware Virus is considered the new STOP/DJVU variant, just like MANW, MZOP, MZQW, ERQW, EROP, ASSM, MZTU (find full list here). This means full data decryption is now possible only if you have been affected by offline encryption key. To decrypt your files, you will have to download Emsisoft Decryptor for STOP DJVU, a tool created and maintained by a genius security researcher Michael Gillespie.
Note! Please do not spam the security researcher with questions whether he can recover your files encrypted with online key - it is not possible.
In order to test the tool and see if it can decrypt KCBU files, follow the given tutorial.
- Download the decryption tool from Emsisoft.
- Click the little arrow next to your download and choose Show in Folder.
- Now, right-click the file and choose Run as Administrator. If asked, enter administrator's password.
- In UAC window, click Yes.
- Click Yes to agree to software terms in both windows.
- The tool will automatically include C:// disk as a location to decrypt. The file recovery tool will prepopulate the locations to scan, including connected data storage drives or network drives. Click Add folder if you wish to add additional locations.
In Options tab, you can choose to keep encrypted file copies. We recommend leaving this option selected, especially if you do not know if the decryption tool will work. - Click Decrypt to start restoring KCBU files. You will see the progress in the Results tab. Here, you can see messages from the tool, such as whether the decryption procedure is successful, or you need to wait for an update.
You might also be informed that online key was used to encrypt your files. In such case, the decryption tool won't work for you, and the only way to recover your files is to use a data backup.
Meanings of decryptor's messages
The KCBU decryption tool might display several different messages after failed attempt to restore your files. You might receive one of the following messages:
Error: Unable to decrypt file with ID: [example ID]
This message typically means that there is no corresponding decryption key in the decryptor's database.
No key for New Variant online ID: [example ID]
Notice: this ID appears to be an online ID, decryption is impossible
This message informs that your files were encrypted with online key, meaning no one else has the same encryption/decryption key pair, therefore data recovery without paying the criminals is impossible.
Result: No key for new variant offline ID: [example ID]
This ID appears to be an offline ID. Decryption may be possible in the future.
If you were informed that an offline key was used, but files could not be restored, it means that the offline decryption key isn't available yet. However, receiving this message is extremely good news, meaning that it might be possible to restore your KCBU extension files in the future. It can take a few months until the decryption key gets found and uploaded to the decryptor. We recommend you to follow updates regarding the decryptable DJVU versions here. We strongly recommend backing up your encrypted data and waiting.
Report Internet crime to legal departments
Victims of KCBU Ransomware Virus should report the Internet crime incident to the official government fraud and scam website according to their country:
- In the United States, go to the On Guard Online website.
- In Australia, go to the SCAMwatch website.
- In Germany, go to the Bundesamt für Sicherheit in der Informationstechnik website.
- In Ireland, go to the An Garda Síochána website.
- In New Zealand, go to the Consumer Affairs Scams website.
- In the United Kingdom, go to the Action Fraud website.
- In Canada, go to the Canadian Anti-Fraud Centre.
- In India, go to Indian National Cybercrime Reporting Portal.
- In France, go to the Agence nationale de la sécurité des systèmes d’information.
If you can't find an authority corresponding to your location on this list, we recommend using any search engine to look up "[your country name] report cyber crime". This should lead you to the right authority website. We also recommend staying away from third-party crime report services that are often paid. It costs nothing to report Internet crime to official authorities.
Another recommendation is to contact your country's or region’s federal police or communications authority.
Frequently Asked Questions
You can only open KCBU files if you have the decryption key, or if you were affected by offline encryption type.
To figure out whether you were affected by offline encryption, please go to C:/SystemID/PersonalID.txt and see if the string inside of it ends in t1. You can also try using Emsisoft Decryptor for STOP/DJVU.
Please follow the guidances provided by the official KCBU decryption tools and believe what they say. If they say it is impossible to decrypt, it really is so. There is no magic tool or human capable of decrypting your files hiding somewhere. Encryption is a technique created to be nearly impossible to decrypt without a special private key (held by the criminals).
We advise scanning with anti-virus, anti-malware, malware removal tools or software like RESTORO to eliminate virus damage on the system. If you do not trust using a single tool, try running one after another. However, we do not recommend keeping several security programs on a computer at once as they can interfere with each other's work.
Beware of fake KCBU decryption tools circulating around the web. Cyber criminals are uploading them to various shady websites, also might be promoting them via suspicious Youtube videos. These programs can infect your computer even more heavily (Trojans, miners, etc.). We suggest being extremely cautious around the web. If there will be an official STOP/DJVU decryption tool available, it will be widely discussed in public media.
Norbert Webb is the head of Geek’s Advice team. He is the chief editor of the website who controls the quality of content published. The man also loves reading cybersecurity news, testing new software and sharing his insights on them. Norbert says that following his passion for information technology was one of the best decisions he has ever made. “I don’t feel like working while I’m doing something I love.” However, the geek has other interests, such as snowboarding and traveling.
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