Already the deterrent effect of the investigation on officials’ willingness to discuss security and foreign policy issues, presumably one purpose of the leak crackdown, has been striking. Some government officials and press advocates say Americans are learning less about their government’s actions.

“People are being cautious,” said one intelligence official who, considering the circumstances, spoke on condition of anonymity. “We’re not doing some of the routine things we usually do,” he added, referring to briefings on American security efforts and subjects in the news.

Gregg Leslie, the interim executive director of the Reporters Committee for Freedom of the Press, an advocacy group, said the effect of the current investigation comes on top of a growing awareness by journalists in the last two years that the government often tracks employees’ e-mail and telephone contacts.

“Reporters are beginning to resort to the old practice of meeting on a park bench to avoid leaving an electronic trail,” he said.

The Senate antileak proposals got strong bipartisan support in the intelligence committee, with only Senator Ron Wyden, Democrat of Oregon, voting against them. But in recent days the proposed bill has been pilloried by former officials and civil liberties groups and has gotten no public support from current intelligence officials, the White House or the House Intelligence Committee.

Critics have pointed out that the new rules would be highly selective, applying only to the intelligence agencies and not to the White House, the State Department — or to Congress itself. In addition, they say, by prohibiting official background briefings by subject-matter experts who do not want to be named publicly, the bill could actually prompt reporters to seek out unofficial sources, leading to more uncontrolled disclosures.

“Everybody in the intelligence world agrees that we have never seen so many high-level leaks,” said Mark M. Lowenthal, a former assistant director of the C.I.A. “But this is the wrong solution.”