A hackathon is a convention or event often set up by hardware manufacturers or software companies, but may include other entities, such as a government. These events are created with a specific goal, such as building proper drivers for a specific hardware component, or finding a solution to security vulnerabilities. Sometimes, they are used to design additional features for an existing software platform (e.g., the famous "like" button used in Facebook was conceived at an internal company hackathon).
The United States government held a hackathon in 2011 to improve city transit systems. Hackathons may even be held for educational or social purposes. They may last anywhere from one day to one week. While the term "hack" has notoriously negative connotations, hackathons are a white hat knowledge creation events, rather than malicious or criminal ones.