Both meanings can be expressed using a phrasal verb. To "hack into" something has the blackhat meaning, whereas to "hack at" or "hack up" something has the whit

Both meanings can be expressed using a phrasal verb. To "hack into" something has the blackhat meaning, whereas to "hack at" or "hack up" something has the whitehat meaning. But to "hack" something, without the particle, only sounds right in the blackhat sense, e.g. "the hack the NSA" or "the hack a website". So I guess the noun "hacker" has the default sense someone who hacks into things/places.