Shellcode is machine code that when executed spawns a shell, sometimes.
Shellcode cannot have any null's in it because it is (usually) treated as a C
string and a null will stop the reading of the string, as it is the string
delimiter. Not all "shellcode" spawns a shell, this has become a more generic
name for a bit of position independant machine readable code that can be directly
executed by the cpu. Shellcode must always be position independant - you cannot
access any values through static addresses, as these address will not be static
in the program that is executing your shellcode - environment variables are the
execption to this rule. Remember to always use the smallest part of a register
possible to avoid null's, and xor is your friend.
