The first place CFD (though not by that name) is actually mentioned would be in Storm Front, I believe. However, there were hints of it stretching back a lot. As far back as the Corporate Intrigue book, there was a mission where Lanier is hiring runners to dig up dirt on a NeoNET site experimenting on AIs. Other than the 'blank name' posts in the fluff, though, the only hints given were mostly on the Jackpoint pages or as background of other tech-related plots, as well as people just mentioning that things were... off with Evo's Mars base.
But yeah, first solid mention is in Storm Front, where they collect all those scattered threads, and Stolen Souls, where they give a solid look at what is happening.