As pressure mounts on firms such as Google, Facebook and Twitter to do more to tackle fake news, some are taking things into their own hands.
Technologist Daniel Sieradski has developed a plug-in - known as BS Detector - that flags up "questionable" websites on Facebook and Twitter.
The plug-in - has appeared in dozens of news feeds, leading some to think it was an official Facebook feature.
It appears Facebook is currently blocking links to the site.
BS Detector is a plug-in that uses a list of fake news sources as its reference point . . .