Felix von Leitner (born 2 August 1973), nicknamed Fefe, is a German IT security expert living in Berlin. He is the main author of the dietlibc, a C standard library. His personal blog posts have received media coverage in Germany.
He played a crucial role in distributing videos of a case of abusive policing on the 2009 Freiheit statt Angst ("Freedom instead of fear") demonstration, that in the end led to the obligation of the Berlin police to wear identification badges.
In 2011, prior to the publification of Mac OS X Lion, he accused Apple of doing too little for its security.