Packing & Crypters

Malware registers Thread Local Storage callbacks that execute before the PE entry point, running anti-debug or unpacking logic that most debuggers miss at startup.

Code that rewrites its own instructions at runtime — decrypting or generating the real logic on the fly so a static disassembly never sees the bytes that actually execute.

Compressing an executable with UPX so its real code and strings are only revealed after a self-unpacking stub runs at load time, defeating naive static analysis.