说明：  如果要在Win2000下实现类似Ping BackDoor for Linux的后门，必须以 sniffer 的方式监听ICMP包，而在win2000下写一个简单的sniffer
(If you want to Win2000 achieve Ping BackDoor for Linux similar to the back door, you must listen ICMP packet sniffer manner, but in the next win2000 write a simple sniffer)