WASHINGTON — LESS than 24 hours after Pfc. Bradley Manning was convicted last week of handing off 250,000 State Department cables and defense documents to WikiLeaks, The Guardian published on its Web site the latest classified material from the leaker of the moment, Edward J. Snowden. That installment included the National Security Agency’s playbook for XKeyscore, a powerful surveillance program enabling the agency’s analysts to monitor and trace Internet searches around the globe.

The cases have provided lots of cable-television drama, from Private Manning’s court-martial to Moscow’s provocative granting of temporary asylum to America’s best-known fugitive. But the deeper lessons lie in how the government is stumbling in its efforts to protect its secrets in the Internet age. Washington has still not heeded two decades of warnings that the best way to protect America’s biggest secrets is to have far fewer of them and to recognize that much of what is stamped “secret” today is widely available on the Internet.

There are certainly some secrets the government needs to protect, but many of the most important clues about revolutions, nuclear transfers and new military sites can be found online, in open chat rooms and commercial satellite photos.

In the early days of the cold war, secrecy seemed simpler. Classified documents were almost all on paper, making it far easier to limit access to officials with top clearances. There were not yet 16 intelligence agencies, much less the post-9/11 directives for them to share information they had once kept “stovepiped,” so that others could not get to it.