This seemed to have been caused by Hubert Farlowe the orginal cause of the Zipcar deaddrops. He posted “So if someone wants me I'l be hiding out, basking in the knowledge that I helped the masses ;)”G+ post. Later it was revealed that the origin of the leak was an Edward Faulle.
Over 1000 codes come out. You can find them here
Thomas Greanias seems to be an author that has some connection with Hank Johnson and Conrad Yeats.
He has published in the past some posts in his own website that seem to relate to Niantic and the story
Conrad Yeats and Hank Johnson spotted in Cape Verde article had this passcode posted in plain view -2sc4nianticx8r3z.
According to Thomas this the result of a decoding from the Ingress Island map done by some Resistance members
Since the publication of his book The Alignment: Ingress Thomas has had ocasionally sessions of Q&A in google+.
Answering correctly to the questions he makes gives the possibility to choose between an activation code or an one use passcode.
These one use passcode have some unique characteristics:
examples CRA44FIELD65AM LCK99ISPIRARE93WB WAK97SHAPER12IU KIC99HUMAN30LJ