From Wikipedia, a white hat:

A white hat (or a white-hat hacker, a whitehat) is an ethical security hacker.[1][2] Ethical hacking is a term meant to imply a broader category than just penetration testing.[3][4] Under the owner's consent, white-hat hackers aim to identify any vulnerabilities or security issues the current system has.[5] The white hat is contrasted with the black hat, a malicious hacker; this definitional dichotomy comes from Western films, where heroic and antagonistic cowboys might traditionally wear a white and a black hat, respectively.[6] There is a third kind of hacker known as a grey hat who hacks with good intentions but at times without permission.[7]

White-hat hackers may also work in teams called "sneakers and/or hacker clubs",[8] red teams, or tiger teams.[9]