Removal instructions for Coharos ransomware

Also Known As: Coharos virus
Distribution: Low
Damage level: Severe

Coharos ransomware removal instructions

What is Coharos?

Coharos is yet another ransomware-type infection from the Djvu family. This malware is designed to stealthily infiltrate computers and encrypt most stored data. During encryption, Coharos appends each filename with the ".coharos" extension (hence its name). For example, "sample.jpg" is renamed to "sample.jpg.coharos". Encrypted data immediately becomes unusable. Coharos also generates a "_readme.txt" text file and stores copies in most existing folders.

The new text file delivers a message stating that data is compromised and that victims must purchase a decryption key to restore it. Unfortunately, this information is accurate. Data is encrypted using an algorithm that generates an individual decryption key for each victim. Cyber criminals intentionally store these keys on a remote server and victims are encouraged to pay ransoms to receive them. The cost of each key is equivalent to $980, however, victims are offered a 50% discount if they contact criminals within the first 72 hours of encryption. Additionally, criminals offer free decryption of one file to 'prove' that they are capable of restoring data, thereby gaining victims' trust. In fact, ransomware developers should never be trusted. Research shows that they are likely to ignore victims once payments are submitted. Paying usually gives no positive result and users are scammed. Therefore, ignore all requests to submit payments or even contact these people. Note that Coharos encrypts data using a so-called "offline key" when the system has no internet connection or the server is not responding. This key is hard-coded and used for multiple encryptions. For this reason, we strongly recommend that you try to restore data with a tool developed by Michael Gillespie. The only other solution is to restore everything from a backup, if one has been created.

Screenshot of a message encouraging users to pay a ransom to decrypt their compromised data:

Coharos decrypt instructions

The internet is full of ransomware-type infections that share similarities with Coharos. The list of examples includes (but is not limited to) BORISHORSE, Q1G, TFlower, and Syrk. Most ransomware-type infections virtually identical behavior: they compromise stored files (usually, by encryption) and make ransom demands. Size of ransom and type of encryption algorithm used are the only major differences. Encryptions are generally performed using algorithms such as AES, RSA, and similar, that generate unique decryption keys. Therefore, data encrypted by ransomware can only be restored by its developers. Ransomware infections are one of the main reasons why you should maintain regular backups, however, store them on a remote server (e.g., Cloud) or unplugged storage device (Flash drive, external hard drive, or similar) - locally stored backups are compromised together with regular data. In fact, you should have multiple backup copies stored in different locations, since there is always chance that storage devices or servers can be damaged.

How did ransomware infect my computer?

The exact way in which developers proliferate Coharos is currently unknown, however, infections of this type are often distributed using spam emails, third party software download sources, fake software updaters and 'cracks', and trojans. Spam email campaigns are used to send hundreds of thousands of emails that contain malicious attachments and messages encouraging recipients to open them. To give the impression of legitimacy and increase the chance of tricking recipients, criminals present attachments as 'important documents' such as invoices, receipts, bills, and similar. Unofficial download sources are also used in a similar matter. Criminals present malicious executables as legitimate software, thereby tricking users to manually download and install malware. Fake updaters and cracks infect computers rather than updating or activating software. Trojans are small, malicious applications that infiltrate systems and inject them with additional malware. In summary, lack of knowledge of these threats and careless behavior are the main reasons for computer infections.

Threat Summary:
Name Coharos virus
Threat Type Ransomware, Crypto Virus, Files locker
Detection Names Avast (Win32:CrypterX-gen [Trj]), BitDefender (Trojan.GenericKD.41567381), ESET-NOD32 (A Variant Of Win32/Kryptik.GVLQ), Kaspersky (Trojan-Ransom.Win32.Stop.cr), Full List (VirusTotal)
Encrypted Files Extension .coharos
Ransom Demanding Message _readme.txt
Ransom Amount $980/$490
Cyber Criminal Contact gorentos@bitmessage.ch, gorentos2@firemail.cc
Symptoms Cannot open files stored on your computer, previously functional files now have a different extension (for example, my.docx.locked). A ransom demand message is displayed on your desktop. Cyber criminals demand payment of a ransom (usually in bitcoins) to unlock your files.
Additional Information This malware is designed to show a fake Windows Update window, modify the Windows "hosts" file (to prevent users from accessing cyber security websites) and inject AZORult trojan into the system.
Distribution methods Infected email attachments (macros), torrent websites, malicious ads, unofficial activation and updating tools.
Damage All files are encrypted and cannot be opened without paying a ransom. Additional password-stealing trojans and malware infections can be installed together with a ransomware infection.
Removal

To eliminate Coharos virus our malware researchers recommend scanning your computer with Spyhunter.
▼ Download Spyhunter
Free scanner checks if your computer is infected. To remove malware, you have to purchase the full version of Spyhunter.

How to protect yourself from ransomware infections?

To prevent ransomware infections, be very cautious when browsing the internet and downloading/installing/updating software. Carefully analyze each email attachment received. Files/links received from suspicious/unrecognizable email addresses should be ignored. The same applies to attachments that are irrelevant or do not concern you. Download your software from official sources only and, if possible, choose direct download links. Proper software maintenance is also paramount. Keep installed applications and operating systems up-to-date, however, use tools provided by the official developer or implemented functions. Third party downloaders/installers/updaters often contain third party applications, and thus these tools should not be used. Be aware that cracking installed applications is illegal (software piracy is a cyber crime). In addition, many cracking tools are fake and, thus, the risk of infection is extremely high. Therefore, activating installed software with third party/illegal tools should never be considered. Have a reputable anti-virus/anti-spyware suite installed and running - these tools detect and eliminate malware before it does any harm. The key to computer safety is caution. If your computer is already infected with Coharos, we recommend running a scan with Spyhunter for Windows to automatically eliminate this ransomware.

Text presented in Coharos ransomware text file :

ATTENTION!

Don't worry, you can return all your files!
All your files like photos, databases, documents and other important are encrypted with strongest encryption and unique key.
The only method of recovering files is to purchase decrypt tool and unique key for you.
This software will decrypt all your encrypted files.
What guarantees you have?
You can send one of your encrypted file from your PC and we decrypt it for free.
But we can decrypt only 1 file for free. File must not contain valuable information.
You can get and look video overview decrypt tool:
hxxps://we.tl/t-dIIHZji8hl
Price of private key and decrypt software is $980.
Discount 50% available if you contact us first 72 hours, that's price for you is $490.
Please note that you'll never restore your data without payment.
Check your e-mail "Spam" or "Junk" folder if you don't get answer more than 6 hours.


To get this software you need write on our e-mail:
gorentos@bitmessage.ch

Reserve e-mail address to contact us:
gorentos2@firemail.cc

Your personal ID:
-

Screenshot of files encrypted by Coharos (".coharos" extension):

Files encrypted by Coharos

Malware researcher Michael Gillespie has developed a decryption tool that might restore your data if it was encrypted using an "offline key". As mentioned, each victim gets a unique decryption key, all of which are stored on remote servers controlled by cyber criminals. These are categorized as "online keys", however, there are cases whereby the infected machine has no Internet connection or the server is timing out/not responding. If this is the case, Coharos will use an "offline encryption key", which is hard-coded. Cyber criminals change offline keys periodically to prevent multiple encryptions with the same key. Meanwhile, Michael Gillespie continually gathers offline keys and updates the decrypter, however, the chances of successful decryption are still very low, since only a very small proportion of "offline keys" have so far been gathered. You can download the decrypter by clicking this link (note that the download link remains identical, even though the decrypter is being continually updated). Your files will be restored only if the list of gathered keys includes the one that was used to encrypt your data.

Screenshot of STOP/Djvu decrypter by Michael Gillespie:

STOP/Djvu ransomware decrypter by Michael Gillespie

As with most ransomware from the Djvu family, Coharos also displays a fake Windows update pop-up during the encryption:

Djvu ransomware family fake update

IMPORTANT NOTE! - As well as encrypting data, ransomware-type infections from the Djvu malware family also install a trojan-type virus called AZORult, which is designed to steal various account credentials. Moreover, this malware family is designed to add a number of entries to the Windows hosts file. The entries contain URLs of various websites, most of which are related to malware removal. This is done to prevent users from accessing malware security websites and seeking help. Our website (PCrisk.com) is also on the list. Removing these entries, however, is simple - you can find detailed instructions in this article (note that, although the steps are shown in the Windows 10 environment, the process is virtually identical on all versions of the Microsoft Windows operating system).

Screenshot of websites added to Windows hosts file:

Tro Ransomware adding websites to Windows Hosts file

Coharos ransomware removal:

Instant automatic removal of Coharos virus: Manual threat removal might be a lengthy and complicated process that requires advanced computer skills. Spyhunter is a professional automatic malware removal tool that is recommended to get rid of Coharos virus. Download it by clicking the button below:
▼ DOWNLOAD Spyhunter By downloading any software listed on this website you agree to our Privacy Policy and Terms of Use. Free scanner checks if your computer is infected. To remove malware, you have to purchase the full version of Spyhunter.

Quick menu:

Step 1

Windows XP and Windows 7 users: Start your computer in Safe Mode. Click Start, click Shut Down, click Restart, click OK. During your computer start process, press the F8 key on your keyboard multiple times until you see the Windows Advanced Option menu, and then select Safe Mode with Networking from the list.

Safe Mode with Networking

Video showing how to start Windows 7 in "Safe Mode with Networking":

Windows 8 users: Start Windows 8 is Safe Mode with Networking - Go to Windows 8 Start Screen, type Advanced, in the search results select Settings. Click Advanced startup options, in the opened "General PC Settings" window, select Advanced startup. Click the "Restart now" button. Your computer will now restart into the "Advanced Startup options menu". Click the "Troubleshoot" button, and then click the "Advanced options" button. In the advanced option screen, click "Startup settings". Click the "Restart" button. Your PC will restart into the Startup Settings screen. Press F5 to boot in Safe Mode with Networking.

Windows 8 Safe Mode with networking

Video showing how to start Windows 8 in "Safe Mode with Networking":

Windows 10 users: Click the Windows logo and select the Power icon. In the opened menu click "Restart" while holding "Shift" button on your keyboard. In the "choose an option" window click on the "Troubleshoot", next select "Advanced options". In the advanced options menu select "Startup Settings" and click on the "Restart" button. In the following window you should click the "F5" button on your keyboard. This will restart your operating system in safe mode with networking.

windows 10 safe mode with networking

Video showing how to start Windows 10 in "Safe Mode with Networking":

Step 2

Log in to the account infected with the Coharos virus. Start your Internet browser and download a legitimate anti-spyware program. Update the anti-spyware software and start a full system scan. Remove all entries detected.

If you cannot start your computer in Safe Mode with Networking, try performing a System Restore.

Video showing how to remove ransomware virus using "Safe Mode with Command Prompt" and "System Restore":

1. During your computer start process, press the F8 key on your keyboard multiple times until the Windows Advanced Options menu appears, and then select Safe Mode with Command Prompt from the list and press ENTER.

Boot your computer in Safe Mode with Command Prompt

2. When Command Prompt mode loads, enter the following line: cd restore and press ENTER.

system restore using command prompt type cd restore

3. Next, type this line: rstrui.exe and press ENTER.

system restore using command prompt rstrui.exe

4. In the opened window, click "Next".

restore system files and settings

5. Select one of the available Restore Points and click "Next" (this will restore your computer system to an earlier time and date, prior to the Coharos ransomware virus infiltrating your PC).

select a restore point

6. In the opened window, click "Yes".

run system restore

7. After restoring your computer to a previous date, download and scan your PC with recommended malware removal software to eliminate any remaining Coharos ransomware files.

To restore individual files encrypted by this ransomware, try using Windows Previous Versions feature. This method is only effective if the System Restore function was enabled on an infected operating system. Note that some variants of Coharos are known to remove Shadow Volume Copies of the files, so this method may not work on all computers.

To restore a file, right-click over it, go into Properties, and select the Previous Versions tab. If the relevant file has a Restore Point, select it and click the "Restore" button.

Restoring files encrypted by CryptoDefense

If you cannot start your computer in Safe Mode with Networking (or with Command Prompt), boot your computer using a rescue disk. Some variants of ransomware disable Safe Mode making its removal complicated. For this step, you require access to another computer.

To regain control of the files encrypted by Coharos, you can also try using a program called Shadow Explorer. More information on how to use this program is available here.

shadow explorer screenshot

To protect your computer from file encryption ransomware such as this, use reputable antivirus and anti-spyware programs. As an extra protection method, you can use programs called HitmanPro.Alert and EasySync CryptoMonitor, which artificially implant group policy objects into the registry to block rogue programs such as Coharos ransomware.

Note that Windows 10 Fall Creators Update includes a "Controlled Folder Access" feature that blocks ransomware attempts to encrypt your files. By default, this feature automatically protects files stored in the Documents, Pictures, Videos, Music, Favorites as well as Desktop folders.

Controll Folder Access

Windows 10 users should install this update to protect their data from ransomware attacks. Here is more information on how to get this update and add an additional protection layer from ransomware infections.

HitmanPro.Alert CryptoGuard - detects encryption of files and neutralises any attempts without need for user-intervention:

hitmanproalert ransomware prevention application

Malwarebytes Anti-Ransomware Beta uses advanced proactive technology that monitors ransomware activity and terminates it immediately - before reaching users' files:

malwarebytes anti-ransomware

  • The best way to avoid damage from ransomware infections is to maintain regular up-to-date backups. More information on online backup solutions and data recovery software Here.

Other tools known to remove Coharos ransomware:

About the author:

Tomas Meskauskas

Tomas Meskauskas - expert security researcher, professional malware analyst.

I am passionate about computer security and technology. I have an experience of over 10 years working in various companies related to computer technical issue solving and Internet security. I have been working as an author and editor for pcrisk.com since 2010. Follow me on Twitter and LinkedIn to stay informed about the latest online security threats. Contact Tomas Meskauskas.

PCrisk security portal is brought by a company RCS LT. Joined forces of security researchers help educate computer users about the latest online security threats. More information about the company RCS LT.

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Malware activity

Global virus and spyware activity level today:

Medium threat activity
Medium

Increased attack rate of infections detected within the last 24 hours.

QR Code
Coharos virus QR code
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Platform: Windows

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