The article specifically mentions snopes and politifact as sources of truth. They can be, but have also been shown to be less than perfect, and do tend to lean left.

Yesterday, twitter was full of pictures of the immigrant kids that Trump put in cages. This morning, we find out that the pictures were taken in 2014. It's a difficult problem because the retractions are never broadcast/retweeted as prevalently as the original fake news.

This is a difficult area, and the stakes are so high that the arms race will doubtless continue. Because the stakes are so high, you are competing with organizations from allied countries as well as non-allied countries, and from multinational corporations and industry groups, all throwing tens of millions of dollars each on think-tanks and lobbying groups, whose main activities are to publish source material that can be used as supporting "facts" for various news stories.