What CS topics do you need to know in order to hack a network, a web server or an Internet portal?

Question

Burglary protection

The question, of course, sounded stupid. But what you need to know in order to be able, for example, to stop the operation of a large site, portal (commercial, state), hack into the PC of some user, stop the operation of his PC, etc. Either attack government resources, steal their data, shut down the network at some enterprise, or break public wifi

Answer 1

These are very different things. In general, you need to be very good at understanding the structure of what you want to break, at all levels.