That is more than likely a variant of the STOP/Djvu ransomware. You may verify that using ID Ransomware if you'd like to: While STOPDecrypter probably won't be able to recover your files yet, it can still be used to get information that may be able to help the creator of STOPDecrypter figure out your decryption key. Here's a link to instructions on how to get this information with STOPDecrypter:   Impo