Cosd Virus Removal Guide (+Decrypt .cosd files)

Cosd – General Info

Cosd is a harmful software application functioning as typical ransomware. Michael Gillespie, the well-known virus researcher, very first discovered this new name in the DJVU ransomware family.

Cosd was developed for the sole function to encrypt all popular file types. Logically, as soon as the encryption is effectively accomplished, the users are not able to get access to them. Cosd ransomware adds its own “.cosd” to all the encrypted files. For instance, the file “price_list.xls”, once modified by Cosd, will be entitled as “price_list.xls.cosd”. When the file encryption is accomplished, Cosd puts its own distinct text file (_readme.txt) into all the folders that store the encrypted files.

The alert mentioned by _readme.txt asking for the random os very comparable to the notices offered by other ransomware threats belonging to the DJVU family. The warning essentially shows that the data has been encrypted and the only solution to get access to it is to use an unique standalone key. Regretfully, this statement is absolutely real.

The method to secure the files utilized by Cosd is not entirely investigated. Nevertheless, there is no doubt that each computer owner might be released a special decryption key, which is absolutely unique. It is very hard to recuperate the information without the suitable key in place.

“Don’t worry, you can return all your files!”, from text file message:

message from Cosd virus

One more peculiarity of the Cosd infection is that the users are unable to get access to the key. The decrypting key is hosted on an unique server under the complete control by the scoundrels who have introduced the Cosd virus into the web. In order to get the key and bring back the important data, the users are informed to connect with the frauds through email or by telegram and to pay the ransom in the quantity of $980.

The message also states that the people must call the Cosd authors within 72 hours upon the minute of the information file encryption. The alert suggests that by doing so the people will get a 50% discount rate, therefore, the ransom quantity drops down to $490.

No matter what the amount of the ransom is, we highly encourage that you do not pay the ransom. There is no guarantee that these online scoundrels will keep their promises, so they may not care at all what the victims feel about the encryption, even when the quantity of the ransom is gotten into their accounts. Thus, paying ransom typically does not lead to a successful healing. So, the users might merely lose their money for nothing.

Similarly, we advise you not to contact the scams as they instruct. Do not move cash into their wallets. There are no applications that could crack the Cosd ransomware or restore the information at no cost. For that reason, the only appropriate decision is to restore the information from possible backups (if available).

Virus Summary

NameCosd Ransomware
File Extensioncosd
Short DescriptionThe ransomware encrypts all the data stored on your system and requires a ransom to be paid on your part supposedly to recover your important files.
SymptomsFile encryption by the ransomware is performed by means of the AES-256 algorithm (CFB mode) encryption algorithm. Once the encryption is completed, the ransomware adds its special .cosd extension to all the files modified by it.
Distribution MethodAdware bundles and software cracks
Similar InfectionsPlam, Pola, Wbxd
Cosd Removal Tool   GridinSoft Anti-Malware
Cosd Decryption Tool   Emsisoft Djvu Decryptor

Do not forget that the Web is now full of infections similar to the Cosd virus. For instance, this particular hazard is basically similar to Brusaf and other ransomware-type infections. These damaging energies have actually been established in order to secure the crucial data and reveal the need for the users to pay the ransom. All these infections use the similar algorithm to create the particular key for effective information decryption.

Unless the Cosd ransomware is still under the advancement procedure or has got some concealed bugs, it is not possible to bring back the data by hand. Hence, the only working option to avoid the loss of your crucial information is to regularly keep updated backups of all your important files.

Another essential piece of suggestions is to store the backups on special storage not linked to your main computer. For instance, you might store it on the USB Flash Drive, or some external hard disk, or by using the cloud data storage services. Keeping the backups on your regular drive is extremely risky, because the backup might also be encrypted by the Cosd infection.

Leakages for the Cosd ransomware attack.

Cosd uses numerous courses to infiltrate the vulnerable computers. It is not particular what particular approach was utilized in your case, however, the invasion might happen by means of the following channels:

  • bundling with third-party programs, mainly free apps;
  • spam emails from the unknown senders;
  • sites providing complimentary hosting;
  • P2P (peer-to-peer) torrent software.

There are times when the Cosd virus might camouflage itself as some authentic application, for instance, through the misleading signals requiring setup of some software application upgrade. This is the most common trick utilized by the scams to inject the Cosd ransomware files into the system. By doing this users partially participate in its installation, without plainly understanding the risk.

In addition, the frauds may send out unsolicited spam e-mail with difficult signals encouraging the people to open suspicious attachments or click some download links, for instance, those encouraging the people to open particular images, text files, tax files and other information.

No doubt, opening these files or clicking on the malicious links may essentially harm the system. Fake Acrobat Reader update alerts may cause the Cosd ransomware infiltration. Similarly, downloading the broken software application may additionally include the ransomware installer. The last but not the least, setup of Cosd may take place through some Trojan horses that may be set up stealthily into the system and without the user’s direct authorization or even consent.

Avoiding the Cosd ransom virus injection.

Naturally, there is no outright guarantee that your computer system will be constantly without any malware attacks, however, we want to share some useful suggestions with you to make it safer. Ensure to pay really very close attention while searching the web and especially while getting cost-free programs. Do not open any suspicious email attachments, especially if the sender is not understood to you.

Do not forget that particular freeware installer might likewise contain some other additional apps in the bundle. These extra applications may be very destructive. It is of utmost importance to keep your anti-virus software and your operating system in basic to be always properly updated.

It is rather rational that downloading cracked apps is illegal, nevertheless, additionally, such unauthorized apps use might likewise bring serious damage to your computer. For this reason, do not download any split programs. Plus, the truth that your current anti-virus did not protect the system from the Cosd ransomware is an excellent reason for you to reassess your options and change to another program that can render the protecting functions on a far better level.

Below please find the quotation from the Cosd text file:

 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:
 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:
 Reserve e-mail address to contact us: 

 Our Telegram account:

Screenshot of files with “.cosd” extension added by the ransomware:”

Cosd Ransomware - encrypt files with .cosd extension

Use GridinSoft Anti-Malware to remove Cosd ransomware from your computer

1.Download GridinSoft Anti-Malware.

You can download GridinSoft Anti-Malware by clicking the button below:

  GridinSoft Anti-Malware

2. Double-click on the setup file.

When setup file has finished downloading, double-click on the setup-antimalware-ag.exe file to install GridinSoft Anti-Malware on your computer.
GridinSoft Anti-Malware
An User Account Control asking you about to allow GridinSoft Anti-Malware to make changes to your device. So, you should click “Yes” to continue with the installation.
GridinSoft Anti-Malware Setup

3. Press Install button for run GridinSoft Anti-Malware.

GridinSoft Anti-Malware Install

3.Once installed, GridinSoft Anti-Malware will automatically run.

GridinSoft Anti-Malware  Start

4. Wait for the GridinSoft Anti-Malware scan to complete.

GridinSoft Anti-Malware will automatically start scanning your computer for Win Speedup 2018 and other malicious programs. This process can take a 20-30 minutes, so we suggest you periodically check on the status of the scan process.
GridinSoft Anti-Malware Scan

5. Click on “Clean Now”.

When the scan has completed, you will see the list of infections that GridinSoft Anti-Malware has detected. To remove them click on the “Clean Now” button in right corner.
GridinSoft Anti-Malware Scan Result

Use Emsisoft Decryptor for restore cosd files

You can download Emsisoft Decryptor by clicking the button below:

  Emsisoft Decryptor

  1. Run the decryptor as an administrator. The license terms will show up, which you have to agree to by clicking the “Yes” button.
  2. Once the license terms are accepted, the primary decryptor user interface opens.
  3. By default, the decryptor will pre-populate the locations to decrypt with the currently connected drives and network drives. Additional locations can be added using the Add” button.
  4. Decryptors typically offer various options depending on the particular malware family. The available options are located in the Options tab and can be enabled or disabled there. You can find a detailed list of the available Options below.
  5. After you have added all the locations you want to decrypt to the list, click the “Decrypt” button to start the decryption process. The screen will switch to a status view, informing you about the current process and decryption status of your files
  6. The decryptor will inform you once the decryption process is finished. If you require the report for your personal records, you can save it by clicking the “Save log” button. You can also copy it straight to your clipboard to paste it into emails or forum posts if you are asked to.
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About Daniel Zimmermann

Daniel Zimmermann has been writing on security and malware subjects for many years and has been working in the security industry for over 10 years. Daniel was educated at the Saarland University in Saarbrücken, Germany and currently lives in New York.

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