Security hacker computers and computer networks, and that cracker is the more appropriate term for those who break into computers, whether computer criminal (black hats) or computer security expert (white hats). A 2014 article concluded that "... the black-hat meaning still prevails among the general public". In computer security, a hacker is someone who focuses on security mechanisms of computer and network systems. While including those who endeavor to strengthen such mechanisms, it is more often used by the mass media and popular culture to refer to those who seek access despite these security measures. That is, the media portrays the 'hacker'
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,