Remove COBA Ransomware Virus (DECRYPT .coba FILES)

remove COBA ransomware virus and learn how to decrypt or repair files with .coba extension (free guide)

COBA ransomware strikes unprotected computers and encrypts data stored in them

Contents

COBA ransomware strikes unprotected computers and encrypts data stored in them
Cybercriminals and ransomware: how these threats are distributed?
Remove COBA ransomware virus and protect your computer
Decrypt COBA files
Frequently Asked Questions

COBA ransomware is a malicious computer virus that has been circling around the Internet for a while. This harmful program is designed to encrypt all files on the target system, making them impossible to open. This piece of malware is a variant of STOP/DJVU ransomware, and this version uses .coba extension to mark encrypted files. For example, files named as 1.docx or 2.png will appear as 1.docx.coba and 2.png.coba after being affected. Going further, the virus creates and saves ransom notes called as _readme.txt to many computer folders.

This virus behaves almost identically to previous versions of STOP/DJVU, such as COSW, GOBA and others. It targets Windows-running computer systems and aims to take files stored in them as hostages. The malware uses encryption to lock data, and then attempts to convince the victim to pay a ransom in exchange for COBA file decryption solution.

To explain the situation for the computer user, the virus leaves ransom notes throughout the system.

Ransom note contents: what do the cybercriminals want?

The ransom note copy can be found in almost each folder containing encrypted data. The message in _readme.txt files is identical, no matter which one the user chooses to open. It explains that all photos, documents, videos, music files and databases have been encrypted. The crooks suggest that the victim can purchase COBA file decryption tool from them, and warn that this tool is the only one capable of reversing damage inflicted on files.

The cybercriminals suggest reaching out to them using provided email addresses: support@freshmail.top or datarestorehelp@airmail.cc. They recommend doing so within 72 hours, as those who meet this condition will receive a 50% discount on the decryption service price. In such situation, the criminals promise to decrypt files for $490 instead of the regular price – $980.

To convince those users who hesitate on paying the ransom, the criminals suggest sending one encrypted file to them for test decryption. However, the user also has to include the Personal ID string that’s provided in the ransom note, as it helps the criminals to identify the victim and pick the right decryption key to use.

However, paying the ransom is not a recommended solution. Cybersecurity experts warn that ransomware victims should not trust cybercriminals as they often do not fulfil their side of the agreement. Even worse, they can start demanding more money. In addition to this, paying money to cybercriminals encourages cybercrime and enables the attackers to employ more people to carry out the illegal operations. Finally, users should know that threat actors often tend to remember victims who are willing to pay the ransom and target them repeatedly.

For more guidance for ransomware victims, please read recommendations issued by FBI and NCSC.

Information-stealing malware dropped alongside the ransomware

This ransomware wreaks havoc on the computer system by encrypting all files, but sadly, that is not the only damage caused by it. On top of that, it carries additional malware alongside it, and these threats are known under the names of Vidar, RedLine, and AZORult. They are known to be information stealers, which means they can be used to extract sensitive information from compromised computers and send it to cybercriminals’ servers. Examples of data that they can steal include passwords, banking information, offline cryptocurrency wallets, browsing history, cookies, computer information, and other details.

The criminals can use such data in a variety of ways, such as blackmailing or hacking of user’s accounts. In addition, these malware variants can allow remote attackers to carry out additional tasks on the computer, such as view or delete files, open command line and run tasks via it, download and run additional malware and more.

Needless to say, computer users should rush to delete such malware from their systems as soon as possible. To remove COBA ransomware virus and additional malware launched alongside it, we recommend using instructions provided by our team of experts. You can find these below the article. Our top pick for malware removal is INTEGO Antivirus, although you can choose any antivirus software you like. However, you may also want to use RESTORO (download link) to scan your computer for virus-damaged files and repair them.

Ransomware Summary

Name	COBA Ransomware Virus
Type	Ransomware; Crypto-malware; Virtual Extortion Virus
Family	STOP/DJVU
Encryption type	RSA 2048 + Salsa20
Previous versions	KAAA, BGJS, BGZQ (find full list here)
Version	660th
Extension	.coba
Cybercriminal emails	support@freshmail.top, datarestorehelp@airmail.cc
Additional malware dropped	Azorult, RedLine or Vidar
Damage	The ransomware uses encryption to maliciously modify all files on the PC and marks their original names with .coba 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, HP/Epson printer drivers, 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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Cybercriminals and ransomware: how these threats are distributed?

Cybercriminals use a variety of methods to distribute ransomware and other threats, although the primary methods are phishing emails with email attachments, rogue online downloads, RDP attacks and exploit kits. When it comes to STOP/DJVU ransomware, the main distribution methods are phishing emails and illegal online downloads, so let’s overview these methods.

The vast majority of COBA ransomware victims report getting infected after attempts to install premium software versions for free. Users who are trying to bypass paying for software license or subscription fee often find themselves visiting shady online websites. These rogue sites claim to provide “100% free and working full software versions” of popular software like Adobe Photoshop, AutoCAD, Wondershare Filmora, and others.

However, the criminals are only using these software names as a bait to convince the victim to open a malicious file that launches a set of malware on the computer. For this reason, computer users should never download cracked software. Please obtain legitimate and genuine software copies from trustworthy and official web resources only.

Another very common ransomware distribution method is email spam. The criminals compose phishing emails to make them look like they were sent by trustworthy companies or organizations. These emails often involve an invite to review some ‘important documents’ such as invoices, order summaries, or missing payments. If the victim falls for this scam and opens the malware-laced attachment, the harmful programs hidden in it can launch immediately.

To avoid getting infected while checking your email, make sure to bypass emails sent by unsolicited senders, and inspect each email with caution. If you notice that the email threatens you about an urgent issue that needs to be solved immediately and rushes you to click on attached files or links, do not do it. Other signs that can reveal malevolent intentions of the sender are overly-generic greeting line that doesn’t include your full name (for example, Dear customer/client/user), grammar and spelling errors in the message, and suspicious-looking sender’s email address.

In general, computer users should exercise caution when browsing the Internet or checking their email, and avoid clicking on something in a rush. Always evaluate whether the content you’re trying to access is likely to be trustworthy or not. In addition, we recommend creating data backups regularly, and installing a trustworthy antivirus with real-time protection feature.

Remove COBA ransomware virus and protect your computer

The instructions prepared by our team will help you to remove COBA ransomware virus and other threats securely. Do not forget to enable real-time protection in your antivirus solution from now on. If you didn’t have such security software so far, we highly recommend options like INTEGO Antivirus. Additionally, you can download RESTORO to repair virus damage on Windows OS.

Once COBA virus removal is finalized, do not forget to overview important security settings on your computer and your personal online accounts. For instance, we recommend changing all of your passwords and enabling 2FA authentication wherever possible.

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COBA 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 COBA 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 COBA 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.

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Decrypt COBA files

Fix and open large COBA 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 COBA 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. COBA Ransomware Virus is considered the new STOP/DJVU variant, just like KAAA, BGJS, BGZQ (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 COBA 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 COBA 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 COBA 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 COBA 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 COBA 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

✓ How can I open .COBA files?

You can only open COBA files if you have the decryption key, or if you were affected by offline encryption type.

✓ How do I know if my files were encrypted with offline or online encryption?

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.

✓ My files contain very important information (family memories). Every tool I used says it is impossible to decrypt. What should I do?

Please follow the guidances provided by the official COBA 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).

✓ I am afraid virus is still in my computer system. What should I do?

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.

✓ I saw several Youtube videos suggesting secret decryption tools. Can I trust them?

Beware of fake COBA 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

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.