The United States is taking "serious and noticeable" measures to prevent another breach of classified files like the massive WikiLeaks document dump, the nation's spy chief said Thursday.

James Clapper, director of national intelligence, said changes were being implemented over the next five years that would create a new security "architecture," making it infinitely harder to disclose America's secrets.

The "terrible event," which saw thousands of US diplomatic and military cables exposed for public scrutiny, "caused us to make some changes," Clapper told a Washington think-tank.

"We have to do more to protect datas and ensure that the information we are giving is actually going to an authorized recipient."

Chief among the changes are improvements in "labeling," and digital "tagging" of diplomatic cables, Clapper said during remarks at the Center for Strategic and International Studies.

At the same time, he said, US officials are eager to ensure information that is intended to be shared can be disseminated without major additional hurdles.

"The goal, of course, is to find that nirvana between the responsibility to share and the need for protection," he said.

Clapper added that the effort aims to protect US secrets not only from outside enemies, but from actors with the system who do not have specific authorization to distribute sensitive US cables and files.

"Frankly we had always responsibility for detecting insider threat. What WikiLeaks has obviously done is heighten our sensitivity about that."

The controversial anti-secrecy WikiLeaks website began releasing US military documents in July 2010. It dumped the entire archive of diplomatic documents in September 2011, causing huge embarrassment to Washington.

A US military tribunal's investigating officer earlier this month recommended that army private Bradley Manning be court-martialed for allegedly funneling hundreds of thousands of classified US documents to WikiLeaks.

Manning, a specialist in US intelligence systems, served in Iraq from November 2009 until his arrest the following May.

He is accused of turning over to WikiLeaks a massive trove of US military reports from Iraq and Afghanistan, some 260,000 classified State Department cables, Guantanamo detainee assessments and videos of US air strikes.