FiB is described as 'The FiB Chrome extension analyzes your Facebook feed for a url, picture, and text's validity. It was built by four students as part of Princeton University's hackathon, with the challenge to solve Facebook's problem with fake news'. There are three alternatives to FiB for a variety of platforms, including Google Chrome, Linux, Mac, Windows and Firefox. The best alternative is B.S. Detector, which is both free and Open Source. Other great apps like FiB are Fake News Monitor (Free) and StB (Free, Open Source).
B.S. Detector is a browser extension that warns users about unreliable news sources. It basically searches all links on a given webpage for references to unreliable sources, checking against a manually compiled list of domains.