I have much better links. Here's one from 2012: Facebook scans chats and posts for criminal activity https://www.cnet.com/news/facebook-scans-chats-and-posts-fo

I have much better links. Here's one from 2012: Facebook scans chats and posts for criminal activity https://www.cnet.com/news/facebook-scans-chats-and-posts-for-criminal-activity/ https://www.cnet.com/news/facebook-scans-chats-and-posts-for... The program probably started a year earlier than that, since in 2011, Facebook announced they were using a tool called PhotoDNA to scan every image shared for underage content. https://www.facebook.com/notes/facebook-safety/meet-the-safety-team/248332788520844/ https://www.facebook.com/notes/facebook-safety/meet-the-safe... Regarding how Facebook crawls links shared in Messenger, there's this medium story I saw on HN a while back https://news.ycombinator.com/item?id=11875419 https://news.ycombinator.com/item?id=11875419 In that medium story, the Facebook devs claim accessing privately shared messenger links is a publicly documented behavior, citing the Facebook Crawler Docs. They quote: "The first time someone shares a link, the Facebook crawler will scrape the HTML at that URL to gather, cache and display info about the content on Facebook like a title, description, and thumbnail image." https://developers.facebook.com/docs/sharing/webmasters/crawler https://developers.facebook.com/docs/sharing/webmasters/craw... I would update my original comment if I could, however the edit period has passed.