/* A simple linux lkm that denies root access to remote users only .
   Might be a good idea to insert such module on a 24/7 connected box
   at night or whenever you're not localy  on the system
   to run compile with gcc -c local0.c;insmod local0.o
   to remove rmmod local0
   tested on redhat 7.2
   Note : on older systems you might have to change
    SYS_setuid32 to SYS_setuid
   by Dalnet SLACKo              slacko@mail.ru                    */
   

#define MODULE
#define __KERNEL__

#include <linux/string.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/config.h>
#include <linux/malloc.h>
#include <asm/uaccess.h>
#include <sys/syscall.h>

extern void *sys_call_table[];
int (*saved)(uid_t);
  
  int my_setuid(uid_t uid) {
  
  int n;
  asm("in %%dx,%%al;":"=a"(n):"a"(0),"d"(0x60));
  if(n != 28 && uid == 0) 
    return -1;
  return saved(uid);
   }

   int init_module() {
  saved = sys_call_table[SYS_setuid32];
  sys_call_table[SYS_setuid32] = my_setuid;
  return 0;
  }
   void cleanup_module() {
  sys_call_table[SYS_setuid32] = saved;
  }