IMAGINE if American citizens never learned about the abuse of prisoners at Abu Ghraib. Imagine not knowing about the brutal treatment of terror suspects at United States government “black sites.” Or about the drone program that is expanding under President Obama, or the Bush administration’s warrantless wiretapping of Americans.

This is a world without leaks.

And a world without leaks — the secret government information slipped to the press — may be the direction we’re headed in. Since 9/11, leakers and whistle-blowers have become an increasingly endangered species. Some, like the former C.I.A. official John Kiriakou, have gone to jail. Another, Pfc. Bradley Manning, is charged with “aiding the enemy” for the masses of classified information he gave to Julian Assange’s WikiLeaks. He could face life in prison.

The government has its reasons for cracking down. Obama administration officials have consistently cited national security concerns and expressed their intention to keep prosecuting leakers.

“The government has legitimate secrets that should remain secrets,” Michael V. Hayden, the former C.I.A. director, said in a telephone interview.