	In 2011, Dutch hackers Jobert Abma and Michiel Prins attempted to find security vulnerabilities in 100 prominent high-tech companies. They discovered flaws in all of the companies, including Facebook, Google, Apple, Microsoft, and Twitter. Dubbing their efforts the "Hack 100", Abma and Prins contacted the at-risk firms. While many firms ignored their disclosure attempts, the COO of Facebook, Sheryl Sandberg, gave the warning to their head of product security, Alex Rice. Rice, Abma and Prins connected, and together with Merijn Terheggen founded HackerOne in 2012. In November 2015, Terheggen stepped down from his role as CEO and was replaced by Marten Mickos.