As a former political staffer who has been working in Canberra since the early 1990s Pezzullo would have learnt how the game was played long ago. Leaks from whistleblowing public servants that have the capacity to embarrass the government are often pursued with a vigour bordering on malevolence.

Strategically placed, but unauthorised, information dumps to favoured journalists that prove to be to the government's advantage, and which some dare suggest may even come from politicians or their minders, are another matter entirely.

Once a few ritualistic phrases, such as "round up the usual suspects" have rung out, the official inquisitors return to their desks, jobs done, never to be heard from again.

The author of a letter to the editor published in Friday's The Canberra Times listed three questions to be put to Pezzullo and any others leading the hue and cry to expose the miscreant who embarrassed the secretary and his minister by passing information on to News Corp's Annika Smethurst.

They were: Was the information Smethurst published of public interest? Had any leaked documents been appropriately classified in the first place? And, what harm was actually done to Australia's national interest?

These are all questions Pezzullo could have addressed off his own bat when he testified before the intelligence and security committee on Wednesday.

He chose, instead, to use the event to call for the head of the leaker. "The person who gave [Smethurst] the document... should go to jail for that".

It is hard not to view this as a blatant and calculated attempt to intimidate any other potential whistleblowers and to ensure they would think twice about talking to media.

At the same time he was dismissing the motivation behind the leak as just another move in what he referred to as "the Canberra game".

This case is an excellent example of the distinction the Australian Strategic Policy Institute's Andrew Davies drew between "official secrets" and "official's secrets" a few weeks ago.

The former are confidences that genuinely do need to be kept as their disclosure would threaten the national interest.

The latter are those obscure and embarrassing factoids that have the capacity to make the great and the good look just as flawed, inept and prone to gaffes as the rest of us.

The power of Pezzullo's utterances to intimidate was clearly recognised by shadow Attorney-General Mark Dreyfus on Thursday.

He said: "He [Pezzullo] doesn't seem to appreciate the intimidatory effect of these raids occurring, or indeed the intimidatory effect of him speaking in the way in which he did at the hearing".

It is to be hoped Pezzullo will heed Dreyfus's well-meant suggestion he "reflect on how he, as the senior national security bureaucrat in Australia, could show more understanding, and more respect, for the role that's played by the media and journalists in Australia".

If we had seen more of this earlier it is possible the current round of intelligence and security committee hearings wouldn't have been necessary in the first place.