shellcode

Etymology

shell + code

noun

1. (computing) A small piece of code, used as the payload of a virus or other malware, that launches a shell so that the attacker can control the compromised computer.
   In ELF executables, there aren't a whole lot of code caves (such as in the PE format), so you are not likely to be able to shove more than just a meager amount of shellcode into existing code slots […] 2016, Ryan "elfmaster" O'Neill, Learning Linux Binary Analysis (page 97)