COSD ransomware isn’t the only malware that affects compromised system; it is known to install a password-stealing AZORULT Trojan alongside it. This Trojan has functionalities that help criminals to steal user’s saved passwords, banking details, cryptocurrency and other sensitive information from the computer. In addition, the ransomware deletes Volume Shadow Copies from the system to prevent the victim from recovering encrypted files easily. Then, it modifies Windows HOSTS file to add a list of domains to block for the user.

The ransomware authors want money for file decryption

COSD ransomware authors use encryption to securely lock your files and prevent you from accessing them; their aim is to convince you to pay a ransom to them in exchange for file decryption tools. This is nothing else but a straightforward extortion. The file created in every affected directory, _readme.txt, holds a message from the attackers. They confirm that all data on the computer has been encrypted using strongest algorithms, and that the victim should write to the criminals’ emails as soon as possible. They also suggest attaching one encrypted file along with victim’s personal ID for test decryption. The crooks suggest a ‘solution’: the victim pays a ransom and files will be set free. According to the note, if the victim writes to the criminals and pays the ransom within 72 hours, the ransom price will be $490. Otherwise, it rises to $980. Of course, the attackers won’t provide their bank details for you; they will ask you to purchase cryptocurrency and transfer the required amount to their virtual wallet address. This helps to preserve attacker’s identity. Paying a ransom for cybercriminals isn’t a good idea because not only it doesn’t guarantee successful data decryption, but it also supports the cybercrime industry. Moreover, paying a ransom for someone might be considered illegal in certain countries, such as USA. The safest way to continue using your computer is to remove COSD ransomware virus from it professionally. For that, we recommend using a powerful anti-malware software of your choice. Next, we recommend scanning with RESTORO to eliminate malicious remains and repair virus damage caused on Windows system files.

THREAT SUMMARY

Ransomware distribution techniques

STOP/DJVU ransomware variants such as COSD, PLAM and others are well-known to hide in illegal torrent downloads. For example, if you decide to search for a cracked software versions in various torrent-sharing websites, you risk getting a file that will land a ransomware on your computer. Developers of this ransomware disguise the malicious executive as a crack or keygen that often gets identified by antivirus or Windows Defender on the computer as malicious. However, users of torrent agents often ignore these warnings, thinking that these are simply ‘false positives’ and there’s nothing to worry about. Keep in mind that you should never ignore these warnings by security programs. Users have reported that they have downloaded this virus alongside fake Adobe Photoshop, video editing software or game cracks as well as KMSPico versions. Our recommendation is to always choose legitimate sources to download programs as it is the only way to get a secure and real copy of the software you need. Besides, it is usually way cheaper than deal with ransomware infection consequences. Another popular technique to spread malware is attaching it to mass-distribution email spam campaigns. In such case, criminals craft convincing messages about missing/pending/overdue payment that needs to be reviewed, or other supposedly important information that needs to be seen. The email attachment holds a malicious script that, once opened, downloads malicious payload from an external source and executes it on victim’s computer. Lately, scammers have started another scam campaign urging users to open attached parcel tracking link or document; Beware of that trying to open these can also land malware on your computer, or at least redirect you to phishing websites. Users should also beware that cybercriminals are using fake Adobe Flash Player update pop-ups to trick users into downloading malicious files. You might encounter these pop-ups while browsing on insecure websites, such as adult-only, gaming or gambling-related domains. Keep in mind that you shouldn’t trust random ads asking you to install something; instead, head to the official developer of the suggested software (such as Adobe) and get the update from there.

Remove COSD ransomware virus safely and decrypt files

Read the guidelines on how to remove COSD ransomware virus down below. You will need to boot your PC in Safe Mode first to disable any malicious processes running on your computer. Next, use a trustworthy anti-malware to remove the virus from the system. Finally, we strongly recommend scanning the system with RESTORO to repair virus damage on the system. Once you finish COSD ransomware virus removal, you can start testing available file recovery/repair tools. You can find a list of them down below along with instructions how to use them. Do not forget to change your login information (such as password) for accounts saved in your browser, because of the password-stealing Trojan’s activity. Finally, report the Internet crime incident to the responsible authority in your country (you can find a list of references below). OUR GEEKS RECOMMEND 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: GeeksAdvice.com editors select recommended products based on their effectiveness. We may earn a commission from affiliate links, at no additional cost to you. Learn more. Get INTEGO ANTIVIRUS for Windows to remove ransomware, Trojans, adware and other spyware and malware variants and protect your PC and network drives 24/7. This VB100-certified security software uses state-of-art technology to provide protection against ransomware, Zero-Day attacks and advanced threats, Intego Web Shield blocks dangerous websites, phishing attacks, malicious downloads and installation of potentially unwanted programs. Use INTEGO Antivirus to remove detected threats from your computer. Read full review here. RESTORO provides a free scan that helps to identify hardware, security and stability issues and presents a comprehensive report which can help you to locate and fix detected issues manually. It is a great PC repair software to use after you remove malware with professional antivirus. The full version of software will fix detected issues and repair virus damage caused to your Windows OS files automatically. RESTORO uses AVIRA scanning engine to detect existing spyware and malware. If any are found, the software will eliminate them. Read full review here.

Method 1. Enter Safe Mode with Networking

Before you try to remove COSD 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 Instructions for Windows 8/8.1/10/11 users Now, you can search for and remove COSD 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.

Method 2. Use System Restore

In order to use System Restore, you must have a system restore point, created either manually or automatically. Instructions for Windows XP/Vista/7 users Instructions for Windows 8/8.1/10/11 users 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.

System Mechanic Ultimate Defense If you’re looking for an all-in-one system maintenance suite that has 7 core components providing powerful real-time protection, on-demand malware removal, system optimization, data recovery, password manager, online privacy protection and secure driver wiping technology. Therefore, due to its wide-range of capabilities, System Mechanic Ultimate Defense deserves Geek’s Advice approval. Get it now for 50% off. You may also be interested in its full review.

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Decrypt COSD files

Fix and open large COSD 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.

STOP/DJVU decryption tool usage guide

STOP/DJVU ransomware versions are grouped into old and new variants. COSD ransomware virus is considered the new STOP/DJVU variant, just like BPTO, ISWR, ISZA, BPSM, ZOUU, MBTF, ZNSM (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 COSD files, follow the given tutorial.

Meanings of decryptor’s messages

The COSD 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 COSD 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.

Victims of COSD 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.