Ulbricht was first connected to "Dread Pirate Roberts" by Gary Alford, an Internal Revenue Service investigator working with the U.S. Drug Enforcement Administration on the Silk Road case, in mid-2013.The connection was made by linking the username "altoid", used during Silk Road's early days to announce the website, and a forum post in which Ulbricht, posting under the nickname "altoid", asked for programming help and gave his email address, which contained his full name.
[1] https://en.wikipedia.org/wiki/Ross_Ulbricht#Arrest