Ransomware Research

Katyusha Ransomware

Katyusha is a malicious ransomware strain that encrypts victim files and demands ransom payment for decryption. First observed in the wild on October 1, 2018, this ransomware has been actively targeting systems worldwide. Security researchers also track this malware under the aliases: Sysfrog.

Quick facts

Ransomware Family
Katyusha
First Seen
October 1, 2018
Known Aliases
Sysfrog

How Katyusha ransomware works

File encryption patterns

Katyusha modifies encrypted files using specific patterns to mark them as encrypted:

Extensions added after encryption
.katyusha.sysfrog
Prefixes added to encrypted files
[sysfrog@protonmail.com]

Ransom note and payment demands

After encrypting files, Katyusha displays ransom notes demanding payment for file recovery:

file_how_to_decrypt_you_files.txt
notes/_how_to_decrypt_you_files.txt
Location: ProgramData
filehow_to_decrypt.txt
notes/how_to_decrypt.txt
Location: ProgramData, RootDiscs

Technical indicators

Associated executable files

The following executable files are associated with Katyusha ransomware:

About this analysis

This Katyusha ransomware analysis is part of Elastio's comprehensive ransomware detection database. Elastio provides advanced ransomware protection and recovery, helping organizations defend against and recover from ransomware attacks like Katyusha.

Last updated: December 30, 2025

Detection coverage

Elastio detects Katyusha inside your data and backups.

The Hunt Engine uses Deep File Inspection to identify Katyusha across live data, replicated data, and backups. If this family is in your environment, Elastio finds it before encryption completes. Run a scan against your recovery points to confirm.

See How the Hunt Engine WorksRequest a Demo

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