What is Kolz file extension .Kolz is a file extension that is used by the 252th version of the STOP ransomware to mark files that have been encrypted. This means that all files with this file extension are encrypted by ransomware, which received the name ‘Kolz ransomware’. Like other ransomware, it is created to encrypt … Continue reading Remove Kolz ransomware. Decrypt .kolz files. Kolz File Recovery.