white hat

1 :  one who is admirable and honorable

2 :  a mark or symbol of goodness could use a few more guys in white hats — Robert Christgau

3 :  a hacker who tests computer systems for possible vulnerabilities so that they can be fixed Chu, 33, is part of a fraternity known as “penetration testers” or “ethical hackers,” a group of experts who are hired to hack into computer systems or find other ways to gain access. These so-called “white hats” will spend days or weeks searching company systems to come up with recommendations for fortifying corporations against such threats. — Greg Wiles — compare black hat