WASHINGTON — Stephen J. Kim, an arms expert who immigrated from South Korea as a child, spent a decade briefing top government officials on the dangers posed by North Korea. Then last August he was charged with violating the Espionage Act — not by aiding some foreign adversary, but by revealing classified information to a Fox News reporter.

Mr. Kim’s case is next in line in the Obama administration’s unprecedented crackdown on leaks, after the crumbling last week of the case against a former National Security Agency official, Thomas A. Drake. Accused of giving secrets to The Baltimore Sun, Mr. Drake pleaded guilty to a minor charge and will serve no prison time and pay no fine.

The Justice Department shows no sign of rethinking its campaign to punish unauthorized disclosures to the news media, with five criminal cases so far under President Obama, compared with three under all previous presidents combined. This week, a grand jury in Virginia heard testimony in a continuing investigation of WikiLeaks, the antisecrecy group, a rare effort to prosecute those who publish secrets, rather than those who leak them.

The string of cases reflects a broad belief across two administrations and in both parties in Congress that leaks have gotten out of hand, endangering intelligence agents and exposing American spying methods.