在表语从句中 此处该用who还是what

问题描述:

在表语从句中 此处该用who还是what
He is ____is known as a hacker- he likes to show off on the Internet and attack website.
在空格处该填who还是what?
为什么?

He,who is known as a hacker- he likes to show off on the Internet and attack website
我只听过这种说法~
he is__is known这种~没有吧.