black hat

noun

1. a villain, as in a cowboy movie; bad guy.
2. Digital Technology. a hacker who violates the security of a system without the knowledge or consent of the owner or developer, as for personal profit or for the gratification of causing damage.

noun

1. informal
   1. a computer hacker who carries out illegal malicious hacking work
   2. (as modifier)black-hat hackers Compare white hat