beating IsDebuggerPresent for my unpacker

[D-Jester]

Code Taken From: Guide on How to play with processes memory, write loaders and Oraculums

http://www.exetools.com/forum/showthread.php?t=6556

Many Thanks to Shub-Nigurrath

unsigned long KillisDebuggerPresent() 
{
	FARPROC addrIDP; //Buffer for API Address IsDebuggerPresent
	
	BYTE rdt[13]; //Buffer to read to (Total of 13 bytes)
    	BYTE wrt[3] = {0x33, 0xC0, 0xC3}; /*(Bytes to write (patch):
						33C0	xor eax, eax
						C3	ret
					  */
	unsigned long byteswritten=0;
	
	DWORD oldpr=0;
	
	HINSTANCE hKer;
	HANDLE hProcess = GetCurrentProcess();
	
	hKer = GetModuleHandle("KERNEL32");
	ZeroMemory(rdt,16);
	
	addrIDP = GetProcAddress(hKer, "IsDebuggerPresent");
	
	VirtualProtectEx(hProcess, (LPVOID)addrIDP, 3, PAGE_READONLY, &oldpr);
	ReadProcessMemory(hProcess, (LPVOID)addrIDP, (LPVOID)rdt, 13, NULL);
	VirtualProtectEx(hProcess, (LPVOID)addrIDP, 3, oldpr, &oldpr);
	
	// Check api signature
	if (rdt[0]==0x64 && rdt[1]==0xA1 && rdt[2]==0x18  && rdt[3]==0 && rdt[4]==0 && rdt[5]==0 && rdt[6]==0x8B && rdt[7]==0x40 && rdt[8]==0x30 && rdt[9]==0x0F && rdt[10]==0xB6 && rdt[11]==0x40 && rdt[12]==0x02) 
	{	
		__asm
		{
			add addrIDP, 9
		}
		
		VirtualProtectEx(hProcess, (LPVOID)addrIDP, 3, PAGE_READWRITE, &oldpr);
		WriteProcessMemory(hProcess, (LPVOID)addrIDP, (LPVOID)wrt, 3, &byteswritten);
		VirtualProtectEx(hProcess, (LPVOID)addrIDP, 3, oldpr, &oldpr);
	}
	return byteswritten;
}

Regards...