What Is Shellcode?

• Shellcode is a small piece of machine code that a payload executes once an attacker gains control of the instruction pointer.
• The name comes from its classic goal: spawning a command shell (e.g., /bin/sh) to give the attacker interactive control.
• Broader meaning today: any self-contained payload code — open a port, add a user, download a stage-2, disable a defense.
• It is the "what happens next" after a vulnerability (like a buffer overflow) hands over control.