Security hacker little reason beyond maliciousness or for personal gain" (Moore, 2005). The term was coined by Richard Stallman, to contrast the maliciousness of a criminal hacker versus the spirit of playfulness and exploration in hacker culture, or the ethos of the white hat hacker who performs hacking duties to identify places to repair or as a means of legitimate employment. Black hat hackers form the stereotypical, illegal hacking groups often portrayed in popular culture, and are "the epitome of all that the public fears in a computer criminal". A grey hat hacker lies between a black hat and a white hat
Severin Hacker that that it would be accessible for non-English speakers. They felt that automated translation software wasn't as effective as using the skills and knowledge of bilingual speakers. During Hacker's doctoral studies, Duolingo became a by-product of this idea, or "happy mistake." Hacker's goal for Duolingo was to make it "100% free" so the most disadvantaged person with an internet connection would still have access to it. Hacker and his team of PhD students used machine learning to personalize Duolingo to each user. Specifically, they wanted to predict what language concepts the user was on the verge of forgetting. In 2012,