Anti DLL Injection

Código:

#include <windows.h>

DWORD g_dwLoadLibraryAJMP;

/* HOOK FUNCTION */

DWORD WINAPI jumphook( DWORD AddressToPerformJump, DWORD AddressOfMyFunction, DWORD LenghOfTheAreaToPerformTheJump )
{
 if( LenghOfTheAreaToPerformTheJump < 5 )
  return 0;

 DWORD RelativeJump, 
    NextInstructionAddress,
    Flag;

 if ( ! VirtualProtect((LPVOID)AddressToPerformJump, LenghOfTheAreaToPerformTheJump, PAGE_EXECUTE_READWRITE, &Flag) )
  return 0;

 NextInstructionAddress = AddressToPerformJump + LenghOfTheAreaToPerformTheJump;

 *(BYTE*)AddressToPerformJump = 0xE9;

 for( DWORD i = 5; i < LenghOfTheAreaToPerformTheJump; i++)
  *(BYTE*)(AddressToPerformJump+i) = 0x90;

 RelativeJump = AddressOfMyFunction - AddressToPerformJump - 0x5;

 *(DWORD*)(AddressToPerformJump + 0x1) = RelativeJump;

 VirtualProtect((LPVOID)AddressToPerformJump, LenghOfTheAreaToPerformTheJump, Flag, &Flag);

 return NextInstructionAddress; 
}

/* END HOOK FUNCTION */

HMODULE WINAPI hLoadLibraryA( LPCSTR lpLibFileName )
{ 
 __asm
 {
  mov eax, dword ptr ss:[esp + 0x18]
  cmp dword ptr ds:[eax-0x12], 0x8B55FF8B
  je erro
 }
 

 if( lpLibFileName )
 {
  if( !strcmp( lpLibFileName, "twain_32.dll" ) )
   __asm jmp g_dwLoadLibraryAJMP
 }   

 return LoadLibraryExA( lpLibFileName, 0, 0 );

erro:

 /* dll injetada */


 ExitProcess( 0 );

 return 0;
}

void ZPerformHooks()
{