Malware
Meow
According to PCrisk, MEOW is ransomware based on other ransomware called CONTI.
Meow is a Windows malware family.
Background
PCrisk reports that MEOW is ransomware derived from the CONTI family. MEOW encrypts files and tacks the ".MEOW" extension onto their names, while also dropping a "readme.txt" ransom note. For instance, it renames "1.jpg" to "1.jpg.MEOW", "2.png" to "2.png.MEOW", and so on.
Source: Malpedia (Fraunhofer FKIE).