Like other ransomware threats, Nefilim encrypts files on the target system using AES-128 and adds NEFILIM, NEPHILIM, MERIN, TRAPGET, MEFILIN, TELEGRAM, SIGARETA, or OFFWHITE  extension to encrypted files. It uses an RSA-2048 public key embedded in the ransomware executable to encrypt the AES encryption key. It also adds a file that includes the ransom note to the root directory, such as C:\NEFILIM-DECRYPT.txt.