The Senate testimony by former FBI director James Comey didn’t offer much new information about his dealings with President Trump, but it did provide useful insights about one thing: who leaks to the media and why.

Railing about leaks – unauthorized tips to the news media – is a favorite pastime in Washington. Elected officials complain about them, and prosecutors try to hunt down their source when it appears classified information was shared, in violation of the law. And while it gets less attention, corporate CEOs are bedeviled by leaks, too.

But Mr. Comey’s testimony revealed a secret: leakers often are senior officials, and their leaking isn’t an accidental or occasional occurrence. It’s part of how they do their jobs every day.

In most discussions about leaks, there’s an assumption that the culprit is a mid-level manager, someone who’s senior enough to have access to newsworthy material but not senior enough to command authority within the organization. So they go to the press to try to influence a policy decision by bringing public attention to it.

Crouched beneath their humble office cubicle, the leaker bravely whispers by phone to a reporter at the Washington Post or The New York Times. Soon thereafter, documents are sent by encrypted email or, in the case of Mr. Comey, shared via a trusted third party, so their origin cannot be traced.

This image of the leaker as a vulnerable insider is reinforced by news outlets that benefit from the leaked material. They maintain the anonymity of the leaker, often in pious language about the First Amendment and a duty to protect sources from reprisals.

But what Mr. Comey’s testimony reveals is that leakers are often senior officials, not lowly managers. And news organizations protect them so they’ll continue to benefit from access to information at the highest levels, beyond the reach of their competitors.

To be sure, some leaks originate from whistleblowers – people who call attention to illegal or improper conduct and need the shield of anonymity that the press can offer. But that description hardly fits Mr. Comey.

There’s often a romantic aura surrounding leakers, too. Leaking is often portrayed as a noble act in service of the truth. Get the information into the sunlight, this thinking goes, and the world will be a better place.

The truth is, leakers often are pursuing a narrow purpose and doing so in a highly calculated manner. For Mr. Comey, it was the appointment of a special prosecutor in the Russian election-meddling probe. It worked.

Of course, leaking also is found in other settings besides government. The corporate world has a long tradition of operating on news tips and speculation. Rumors of events like acquisitions, buyouts, regulatory investigations, new products and executive appointments to name but a few are all fueled by leaks. And often their source is a CEO or a senior executive at an investment bank or law firm.

Leakers know exactly what they want to accomplish. Many are skilled bureaucratic fighters, and leaking to the press is simply one tactic among many they use to pursue their aims.

We can thank Mr. Comey for educating us on that.