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 Djvu family. This malware is designed to stealthily infiltrate computers and encrypt most of stored data. While encrypting, Coharos appends each filename with ".coharos" extension (thus, its name). For instance, this ransomware would rename "sample.jpg" to "sample.jpg.coharos" and so forth. Encrypted data instantly becomes unusable. Coharos also generates "_readme.txt" text file and drops its copies in almost all existing folders.

The created text file delivers a message stating that data is compromised and that victims must purchase a decryption key in order to restore it. Unfortunately, the fact that decryption requires a unique key is true. Data is encrypted by using an algorithm that generates an individual decryption key for each victim. Cyber criminals intentionally store these keys in a remote server. For this reason, victims have to pay a ransom in order to receive them. Each key costs $980. However, victims will get a 50% discount if they'll contact crooks within first 72 hours after the encryption. Additionally, crooks offer a free decryption of one file. They do this with the intention of proving that they're actually capable of restoring data and gaining victim's trust. Nevertheless, ransomware developers should never be trusted. Research results show that cyber criminals are very likely to ignore victims once payments are submitted. In other words, paying usually gives no positive result and users merely get scammed. For this reason, all encouragements to submit payments and even contact these persons should be ignored. Now it is very important to mention that Coharos encrypts data by using a so-called "offline key" whenever 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 highly recommend to try restoring data with a tool developed by Michael Gillespie. The only other solution is to restore everything from a backup, if there is one created.

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

Coharos decrypt instructions

Internet is full of ransomware-type infections that share similarities with Coharos. The list of examples includes (but it is not limited to) BORISHORSE, Q1G, TFlower, and Syrk. Vast majority of ransomware-type infections behave virtually the same: they compromise stored files (usually, by encrypting) and make ransom demands. Most of the time size of ransom and type of encryption algorithm used are the only major differences. Now the problem is that encryptions are usually performed using algorithms like AES, RSA, and similar that generate unique decryption keys. Therefore, data encrypted by a flawless ransomware can only be restored by its developers. Ransomware infections are one of the main reasons why you should maintain regular data backups. However, be sure to store them in a remote server (e.g., Cloud) or either unplugged storage device (flash drive, external hard drive, or similar) - locally stored backups will be compromised alongside with regular data. In fact, you should have multiple backup copies stored in different locations, since there's always a chance that used storage device or server will be damaged.

How did ransomware infect my computer?

The exact way developers proliferate Coharos is currently unknown. However, it is worth mentioning that infections of this type are often distributed using spam emails, third party software download sources, fake software updaters/cracks, and trojans. Email spam campaigns are used to send hundreds of thousands of emails that contain malicious attachments and messages encouraging recipients to open. In order to create the impression of legitimacy and increase the chance of tricking recipients crooks present attachments as various important documents, such as invoices, receipts, bills, and similar. Unofficial download sources are also used in a similar matter. Crooks present malicious executables as legitimate software, thereby tricking users to download and install malware manually. Next go fake updaters and cracks that infect computers instead of serving their actual purpose, which is updating/activating software. Last, but certainly not least, are trojans. These are small malicious applications designed to infiltrate systems and inject them with additional malware. In summary, the lack of knowledge and reckless behavior are the main reasons for computer infections.

Threat Summary:
Name Coharos virus
Threat Type Ransomware, Crypto Virus, Files locker
Encrypted Files Extension .coharos
Ransom Demanding Message _readme.txt
Ransom Amount $980/$490
Cyber Criminal Contact gorentos@bitmessage.ch, gorentos2@firemail.cc
Symptoms Can't open files stored on your computer, previously functional files now have a different extension, for example my.docx.locked. A ransom demanding message is displayed on your desktop. Cyber criminals are asking to pay a ransom (usually in bitcoins) to unlock your files.
Additional Information This malware is designed to show fake Windows Update window, modify 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?

In order to prevent ransomware infections users must be very cautious when browsing the Internet, as well as downloading/installing/updating software. Always be sure to carefully analyze every single email attachment received. Files/links received from suspicious/unrecognizable email addresses should be ignored. Same goes for attachments that are irrelevant and do not concern you. Download desired software only from official sources and, if possible, choose direct download links. Proper software maintenance is also paramount, which means that you should always keep installed applications/operating system up-to-date. To achieve this use tools provided by the official developer or implemented functions only. It is known that third party downloaders/installers/updaters are likely to contain third party applications, which is why such tools shouldn't be used. Every user should know that cracking installed applications is illegal (software piracy is a cyber crime). If that wasn't enough, vast majority of cracking tools are fake and, thus, the risk of infections is extremely high. Therefore, activating installed software with third party/illegal tools should never be considered. Ultimately, you should always have a reputable anti-virus/anti-spyware suite installed and running - tools of this type are more than likely to detect and eliminate malware before it manages to do 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's 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 we've already mentioned, each victim gets a unique decryption key and all of them are stored in remote servers controlled by cyber criminals. These are categorized as "online keys". However, there are cases when the infected machine has no Internet connection or the server is timing out/not responding. If that is the case, Coharos will use an "offline encryption key", which is hard-coded. Now it is worth mentioning that cyber criminals change offline keys every now and again. This is being done 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 portion of "offline keys" has been gathered. You can download the decrypter by clicking this link (note that the download link remains the same, despite the fact that decrypter is being continually updated). Your files will be restored only if the list of gathered keys will include 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 of ransomware from Djvu family, Coharos also displays a fake Windows update pop-up during the encryption:

Djvu ransomware family fake update

IMPORTANT NOTE! - Aside from encrypting data, ransomware-type infections from Djvu malware family also installs 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 carried out with the intention of making users unable to access malware security websites and seek 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 "Controlled Folder Access" feature that blocks ransomware attempts to encrypt your files. By default this feature automatically protects files stored in 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's more information on how to get this update and add 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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