I DM online, in OpenRPG or WebRPG and over email, and this is one of my favorite advantages of the format. The players can't see what books I have in front of me, so they don't know what adventures, monsters, or other sources I am using.
So no, I don't tell them when, or even if, they are involved in a published adventure. When it is over, I usually give kudos to the creator of the adventure, and give them a general idea of which parts I used.