If you're interested in learning the kind of particular skills used, there's a whole subculture in computer security having to do with Capture the Flags (CTFs), for a rather broad concept of "flag".

https://microcorruption.com/ is a quite a good one to get started with. (Because embedded systems are smaller and do less, they are easier to reason about, which makes it easier to see vulnerabilities.)

See also: https://www.reddit.com/r/securityCTF/

More broadly, the (with-permission) attackers are known as "the Red Team", and the concept is used against computer networks as well as in literal war-games by the US government.