The Null are an extremely intelligent, highly advanced species with access to the network, which has been utilized in Hadriel as a primary communication method for years. They have algorithms to identify people based on video and audio data. Furthermore, during the Null posts, everyone who responded to their initial posts did so with their name attached. Cross referencing the names with previous post history and accessing their inbox would be simple enough. And finally, with access to the network and phone devices, the Null have been capable of, essentially turning on your webcam to get visual data if all else fails and your character never uses the network for whatever reason.

Should have put some tape over that camera I guess!