Shellcode

Shellcode

We have referred to “arbitrary code” up till now to refer to the code that
will be run on the machine. This is usually referred to as Shellcode.
Shellcode is machine executable code in hexadecimal format which
contains the commands to execute on the vulnerable system. This is
usually to spawn a shell on the system (hence the name).
As with the exploit itself, the Shellcode is machine and operating
system dependant. With most buffer overflows, this code is pushed
onto the stack into one of the buffers. Shellcode for many different
systems can be copied from various buffer overflow exploits available
on the Internet. Or it can be created manually by writing the code
which executes a shell, compiling it, and using the hexadecimal
representation as the Shellcode.