原理：

1. 将进程的所有线程的线程CrossThreadFlags标志位设置成Terminated或者System.

效果：任务管理器，WSYSCheck，ICESWORD无法结束进程。。

但PCHunter 可以结束受保护的进程。但PCHunter无法用普通方法结束受保护的线程，必须使用强制结束线程才可结束线程。。

代码：

VOID SetThreadFlagToTerminatedByThreadID(ULONG dwThreadID)
{
	ULONG ulFlagOffset;
	NTSTATUS status = STATUS_UNSUCCESSFUL;
	PULONG pFlag;
	PETHREAD eThead;
	HANDLE threadHandle;


	__try{
		threadHandle = (HANDLE)dwThreadID;
		ulFlagOffset = GetCrossThreadFlagOffset();
		//dprintf("[ProtectProcess]GetCrossThreadFlagOffset: 0X%08X\r\n", ulFlagOffset);

		status = PsLookupThreadByThreadId(threadHandle, &eThead);
		if(!NT_SUCCESS(status))
		{

			dprintf("PsLookupThreadByThreadId ERRORid:0X%08X, TID: 0X%08X\r\n", status, dwThreadID);
			return status;
		}
		//dprintf("ETHREAD:0X%08X\n", eThead);

		pFlag = (ULONG*)((PUCHAR)eThead + ulFlagOffset);
		//dprintf("ulFlag address:0X%08X value:0x%08X\n", pFlag, *pFlag);

		*pFlag |= PS_CROSS_THREAD_FLAGS_TERMINATED;
		dprintf("new ulFlag address:0X%08X value:0x%08X\n", pFlag, *pFlag);
	}__except(EXCEPTION_EXECUTE_HANDLER)
	{
		dprintf("EXCEPTION ON set thread cross flags!");
		return status;
	}
}

http://download.csdn.net/detail/xiaocaiju/8192897

进程保护--CrossThreadFlags标志位