Copy of Typical Sequence Of Antidebug Tricks by waleedassar; source: https://waleedassar.blogspot.com/2012/11/hidding-threads-from-debuggers.html

antidebug.c

//http://waleedassar.blogspot.com 
//http://www.twitter.com/waleedassar
#include "stdafx.h"
#include "windows.h"
#include "iostream.h"


extern "C"
{
       int __stdcall ZwSetInformationThread(HANDLE,int,unsigned long*,unsigned long);
       int __stdcall ZwQueryInformationProcess(HANDLE,int,unsigned long*,unsigned long,unsigned long*);
}

#define ThreadHideFromDebugger 0x11
#define ProcessDebugPort   0x7
#define ProcessDebugObjectHandle 0x1E
#define ProcessDebugFlags 0x1F

int main(int argc, char* argv[])
{
	//------------------------------------
	unsigned long _port_=0;
	ZwQueryInformationProcess(GetCurrentProcess(),ProcessDebugPort,&_port_,0x4,0);
	if(_port_)
	{
		MessageBox(0,"BeingDebugged","waliedassar",0);
		ExitProcess(-1);
	}
	//------------------------------------
	unsigned long DbgObjHand=0;
	int ret=ZwQueryInformationProcess(GetCurrentProcess(),ProcessDebugObjectHandle,&DbgObjHand,0x4,0);
	if(ret>=0 || DbgObjHand)
	{
		MessageBox(0,"BeingDebugged","waliedassar",0);
		ExitProcess(-2);
	}
	//------------------------------------
	unsigned long DbgFlags=0;
	ZwQueryInformationProcess(GetCurrentProcess(),ProcessDebugFlags,&DbgFlags,0x4,0);
	if(DbgFlags==0)
	{
            //Only if Process was spawned by the "DEBUG_ONLY_THIS_PROCESS" flag of
            //The "CreateProcess" function i.e. No Child Debugging.
            //Does not harm you code, though.
	    MessageBox(0,"BeingDebugged","waliedassar",0);
		ExitProcess(-2);
	}
	//------------------------------------
	ZwSetInformationThread(GetCurrentThread(),ThreadHideFromDebugger,0,0);
	

	MessageBox(0,"Can you see me under debugger","waliedassar",0);
	return 0;
}