Speaking at the Lowy Institute, Mr Warner touched very lightly on a number of subjects without giving away any secrets. In fact this is the first time the head of ASIS (Australian Security Intelligence Service; similar in role to the more-familiar CIA and MI6) has ever spoken publicly.
Note that it is a Federal offence to identify any employee of ASIS other than Mr Warner, its head.
In much the same way as undercover police are finding it more and more difficult to establish and maintain their undercover persona (as ex-AFP Commissioner Mick Keelty noted at the 2011 Security Conference in Sydney), the indelible digital trace we leave across the Internet is very difficult to either modify or fake.
These days, it isn't hard to unearth all kinds of historical trivia about anyone; so easy in fact that the lack of such detritus is, of itself, remarkably suspicious.
Better still, with the abundance of facial recognition systems (including, but not limited to Facebook), it would be rather wise that his face didn't appear in any police or military graduation ceremonies.
Of course the proliferation of digital technologies are a two-edged sword as Warner notes, "The separate yet inter-related revolutions underway in information technology, nanotechnology, biometrics and materials technology will also fundamentally alter the environment in which our officers operate.
"Developments in cyber are a two-edged sword for an agency like ASIS. They offer new ways of collecting information, but the digital fingerprints and footprints which we all now leave behind complicate the task of operating covertly."
Memo to all budding undercover spies: start creating your second (false) digital persona the day you're born - you'll probably need it. Oh and only get photographed with the people that you plan on going under-cover with.