While Russian disinformation aimed at last year's US election is getting the most focus, there's been no larger arena for a sustained disinformation campaign than Syria (MH17 probably got a more intense version of the same, but it hasn't lasted as long). From the beginning, an effort to obscure Bashar al-Assad involvement in atrocities, most notably usage of chemical weapons, and to characterize his opposition as either ISIS or too weak be deserving of external support.
As a minor but recent episode in this campaign, consider the case of Thamer al-Sabhan. He has had what is essentially a journeyman career in Saudi politics, from a very brief stint as ambassador to Iraq to Minister of State for Gulf Affairs -- a non-existent position in Saudi officialdom until it was created to ease him out of the Iraq job.
But if you read certain sections of online media, he's not just a mid-level, mid-career Saudi diplomat, in fact a mastermind and instigator of a Saudi multi-front campaign against Hezbollah and all its allied militias, and is catapulting the region towards a major war as a result of his activities. Here's an example of a Twitter thread where al-Sabhan predictably appears (about half-way down) as the boogeyman -- a thread that includes widely cited Syria expert Joshua Landis. And the "evidence" for all this is simply some excitable quotes from al-Sabhan, which never convey his relative influence on the Saudi government.
And while he's been a hate figure in Syria commentary for some time, what elevated him in the last few weeks to this exalted status? News reports that he had visited Raqqa with US envoy Brett McGurk, which were then hyped up by Iranian official and semi-official media to stoke "outrage," which the Twitter commentariat duly supplied.
Meanwhile, aid conditions in Syria are getting worse, and there's still been no accountability on the government for any of crimes of the last six years. But people on Twitter are ready to sigh and move on.