Usually people use firewall to block the ports to prevent hackers.
But I think we can try an opposite way.

在武俠小說裡 真正厲害的人 你是看不出他在防守的

1. Imaging that when you scan a computer's ports, every ports from 1 to 9999999... are all opened.

2. When you want to test each port, you'll fire the alarm.