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Remove Kostya Virus and Restore .k0stya Files


Kostya is the name of a Czech ransomware cryptovirus. The ransom message that it displays is written in the Czech language and has a skull with the name “Kostya” shown on top. The virus claims in this ransom note that it encrypts files with a 256-bit AES algorithm. Locked files will have the extension .k0stya appended to them. To see how to remove the ransomware and how you can try to restore your data, carefully read the article.

Threat Summary

NameKostya Virus
TypeRansomware, Cryptovirus
Short DescriptionThe ransomware will encrypt your files with an AES 256-bit encryption. Then it will display a ransom note with the name “Kostya” displayed on top.
SymptomsThe ransomware will display a ransom note written in Czech and lock files with the .k0stya extension appended to them.
Distribution MethodSpam Emails, Email Attachments
Detection Tool See If Your System Has Been Affected by Kostya Virus


Malware Removal Tool

User ExperienceJoin Our Forum to Discuss Kostya Virus.
Data Recovery ToolWindows Data Recovery by Stellar Phoenix Notice! This product scans your drive sectors to recover lost files and it may not recover 100% of the encrypted files, but only few of them, depending on the situation and whether or not you have reformatted your drive.

Kostya Virus – Infection Spread

Kostya ransomware could infect your computer using various spread methods. Spam emails could be responsible for spreading its payload file. An email involved in spam campaigns will be devised to make you think that something very important is in the attachment of that electronic letter. In reality, the attached file will indeed look as what is described in the email, namely a legitimate document, invoice or something similar. Upon opening it, however, the malicious code from the file will infect your computer device with the virus.

Extra ways of infection for the Kostya ransomware could exist. For instance – ways that make use of sharing files on special sharing services and social media outlets. The ransomware maker might have put the malicious payload file on other such platforms to try and infect more potential victims. While browsing the Internet, try to be warier. Don’t open files from suspicious emails or links. Scan files with a security program and check their signatures and size before opening. You should read more tips on preventing ransomware from our forum thread.

Kostya Virus – Technical Analysis

Researchers have found Kostya ransomware recently. The ransom note is written entirely in Czech and looks very much like a variant of the previous Czech ransomware virus.

When the Kostya ransomware executes its payload file, it can create entries in the Windows Registry to remain persistent. Entries like that are usually designed in a way to make the virus start automatically with each boot of the Windows operating system. After that your files get encrypted, and then a lock-screen with the ransom message is displayed on your desktop. The entire ransom note is written in the Czech language. You can view it from the picture below:


Part of the original text in Czech reads:

Pokud čtete tuto zprávu, stále si můžete obnovit své soubory! Stačí zakoupit kartu PaySafe Card v hodnotě 300 Kč a poslat kód (číslo), email:še platba bude přezkoumána.Po ověření své soubory a počítač do původního stavu během 24 hodin.

A rough translation of that message in English:

If you are reading this message, you can still recover your files! Just purchase a Paysafe Card in the amount of CZK 300 and send the code (number), email:
Your payment will be reviewed.
After verifying your files and your computer to its original state within 24 hours.

The Kostya virus uses the email address which is provided as a contact with the cybercriminals. Here, the encrypted electronic mail service ProtonMail is used once again by ransomware developers. That trend might continue to increase as that makes it harder for officers of the law to catch the crooks.

The Kostya ransomware does not give you a deadline to decrypt your data, but the amount of 300 CZK is demanded to be paid. That amount equals to twelve US dollars. However, if you do not pay that sum within a 12-hour time frame, the price will rise to 2000 CZK or 86 US dollars. You shouldn’t think of paying the cyber crooks, no matter how small the asked ransom price is. Nobody can guarantee you the full recovery of your data after payment. The criminals will use the financial support to fund a new ransomware campaign or some other criminal activity.

The following file types become encrypted:

→.as, .as3, .asf, .asp, .asx, .txt, .bay, .bmp, .cdr, .cer, .class, .pp, .png, .3dm, .3g2, .3gp, .aaf, .accdb, .aep, .aepx, .aet, .ai, .aif, .arw, .cr2, .crt, .crw, .cs, .csv, .db, .dbf, .veg, .dcr, .der, .dng, .doc, .docb, .docm, .vcf, .vob, .wb2, .wma, .wmv, .wpd, .wps, .x3f, .xla, .xlam, .xlk, .kdc, .m3u, .m3u8, .m4u, .max, .mdb, .mdf, .mef, .mid, .mp3, .docx, .dot, .dotm, .dotx, .dwg, .bak, .pub, .tar, .dxf, .dxg, .efx, .eps, .erf, .fla, .idml, .iff, .indb, .indd, .config, .csproj, .vbproj, .vb, .sln, .suo, .indl, .class, .indt, .inx, .jar, .java, .jpeg, .jpg, .potm, .potx, .ppam, .ppj, .pps, .xaml, .ppsm, .torrent, .proj, .ppsx, .ppt, .pptm, .pptx, .prel, .rw2, .rwl, .ico, .sdf, .sldm, .cache, .sldx, .dll, .sql, .sr2, .srf, .cert, .srw, .tif, .mpa, .resources, .resx, .mpg, .mrw, .msg, .nef, .nrw, .odb, .odc, .odm, .odp, .ods, .odt, .orf, .p12, .p7b, .p7c, .pdb, .pdf, .js, .cad, .json, .pef, .pem, .pfx, ., .php, ., .plb, .pmd, .pot, .prproj, .ps, .psd, .pst, .ptx, .r3d, .pst, .mpp, .ra, .raf, .css, .raw, .rb, .rtf, .html, .xll, .xlm, .xls, .xlsb, .xlsm, .xlsx, .xlt, .xltm, .xltx, .xlw, .xml, .xqx

Any file that has one of the above extensions will certainly become locked. All encrypted files will have the .k0stya extension appended to them, after the original file extension. The ransomware utilizes a 256-bit AES encryption algorithm. That is at least what is stated in its ransom message.

The Kostya ransomware is more than likely to erase all Shadow Volume Copies from the Windows operating system. The interesting thing is that only the C partition of the system is encrypted. Continue to read and see ways with which you can try to restore some of your data.

Remove Kostya Virus and Restore .k0stya Files

If your computer got infected with the Kostya ransomware virus, you should have some experience in removing malware. You should get rid of this ransomware as fast as possible before it can have the chance to spread further and infect more computers. You should remove the ransomware and follow the step-by-step instructions guide given below. To see ways that you can try to recover your data, see the step titled 2. Restore files encrypted by Kostya Virus.


Berta Bilbao

Berta is a dedicated malware researcher, dreaming for a more secure cyber space. Her fascination with IT security began a few years ago when a malware locked her out of her own computer.

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