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.

“网络卫士”在中文中的名称叫做“白客”,也就是“黑客”的反义词。“白客”指在网络世界中打击黑客以保护人们信息安全的网络专业人员。很多白客以前都曾经充当过黑客，这是大家都见怪不怪的事实。

For example:

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

我认识一位白客，他之前为军方工作过，能在十分钟内潜入任何电脑。