One thing to remember when people complain about national security information being leaked is Nixon's experience with such things.
The whole apparatus that led to Watergate being possible of course was caused by concerns over leaks, in particular the formation of a semi-plausibly deniable unit composed primarily of former assets of the U.S. government known as the Plumbers, which of course was called that to plug leaks of the scale of the Pentagon Papers.
Those on the Left can't complain too much about leaks, since they thought Nixon was wrong to harrass Daniel Ellsberg over that release, if one could argue that in a middle of a war, Ellsberg in fact did give aid and comfort to the Vietminh Liberation Front and their North Vietnamese patrons.
On the other hand, the main thing the Pentagon Papers revealed were internal U.S. policy debates over the Vietnam engagement and doubts therein, if that did possibly increase enemy morale net by having that acknowledged in the way that it was, since the North Vietnamese had no scruples about executing those who opposed their war effort.
That right there is the key thing to remember, the lack of dissent in some States having any mechanism of expression whatsoever, as the formation of national security policy poses fairly intractable issues for a Republic because of that unpleasant fact of life: ask a Syrian or Iraqi about what Baathists are like on that point of mechanism of dissent.
That dilemma that inevitably leads to leaking is because in a Republic like ours, the government attempts in a serious fashion to rule in the name of the people, and yet must deal with other governments who make no such effort, other than propagandizing for regime survival.
We do that too of course, but the qualitative difference remains important, indeed decisive, as to consequences.
That lack of dissent mechanism in many parts of the world makes it rather easy, and understandable, to argue that to have open American debate over too much material would not be in the interest of the People the Government is attempting to serve, even as that's a rather easy rationalization for a national security bureaucracy that is every bit as dangerously unaccountable as its granted enemies, and frenemies, overseas.
Thus, if the argument about enemies abroad makes people want to classify everything as "Secret," "Top Secret," "Top Secret/Selectively Compartmented Information," etc.., (a system by the way which in itself creates a difficulty of getting outside opinion due to the expense of clearing someone at various levels), since the overclassification is well-understood, that leads to a powerful counter-tendency, which is to leak things, especially when policy is being debated.
That's a big part of what transpired with Wiki Leaks as to functionality, whatever one thinks of that whole affair, if its really also in the movie Burn After Reading as to the whole thing being pointless in terms of the Russians saying,"I could read this in the newspaper, you must be joking."
When one adds on to that fact that over-classification is understood, the incentive to release information to signal governments overseas at times, combined with the symbiotic "access" relationship of elected and non-elected govermental officials with the media, "background," then one can predict that people will leak information, with formal authorization or not.
Those reasons may be good, "People (Iran) need to know this," bad,"That's good for my career," or ugly, "That's how I win that policy debate," but as to leaking, its as old as time, for reasons one can see as far back as Nixon more evidently.