The phrase “online security guard”, which literally means “white clan” in Chinese, is the opposite of “black clan” or hacker. It refers to professionals who fight hackers in order to protect people’s information security in the online world. It’s not unusual that some of the online security guards are former hackers.

“網絡衛士”在中文中的名稱叫做“白客”,也就是“黑客”的反義詞。“白客”指在網絡世界中打擊黑客以保護人們信息安全的網絡專業人員。很多白客以前都曾經充當過黑客，這是大家都見怪不怪的事實。

For example:

I know an online security guard who used to work for the military, he can break into any computer in 10 minutes.

我認識一位白客，他之前為軍方工作過，能在十分鐘內潛入任何電腦。