Adversaries may perform software packing to conceal their code. Software packing is a method of compressing or encrypting an executable. Packing an executable changes the file signature in an attempt to avoid signature-based detection. Most decompression techniques decompress the executable code in memory.
Utilities used to perform software packing are called packers. An example packer is FTT. A more comprehensive list of known packers is available, but adversaries may create their own packing techniques that do not leave the same artifacts as well-known packers to evade defenses.
This type of attack technique cannot be easily mitigated with preventive controls since it is based on the abuse of system features.
Application vetting services could look for known software packers or artifacts of packing techniques. Packing is not a definitive indicator of malicious activity, because as legitimate software may use packing techniques to reduce binary size or to protect proprietary code.