The current populous malwares are mostly obfuscated, packed, or encrypted to thwart detection and impede reverse engineering, usually as way to buy more time so that analysis will be made redundant if the malware has achieved its goals. However, while packed/encrypted malwares have telltale signs, such as high entropy or PE format anomalies, obfuscation can be trickier to detect in the first place – undocumented function calls, singular call gates, environment aware malware, and ingenious methods to bypass both static and automated dynamic analysis, among various other techniques, are very much in vogue. Some foundational unpacking skills are certainly a necessity that every malware analyst must be well acquainted with.

Packers such as Ultimate Packer for Executables (UPX) are more of executable compressors as size reduction is the primary goal, not obfuscation, which can be a byproduct of customizing the open source code to create altered variants. Think of a...