StB is described as 'Chrome browser extension to block websites that publish fake news'. There are three alternatives to StB 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 StB are Fake News Monitor (Free) and FiB (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.
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.