Code or code fragments for various operating systems that can be pasted onto buffer overflow exploits. When crackers successfully exploit vulnerabilities such as buffer overflows, they typically open a shell at the end of the exploit. With a command-line shell, the cracker then can perform any task he or she desires. However, opening shells within buffer overflow exploits can be difficult. For this reason, crackers often maintain libraries of shellcode.

See Also: Buffer Overflows; Crackers; Shell.