It's an adage in intelligence circles: Failures are open for all the world to see; successes stay secret forever. On Thursday, CIA Director George Tenet (search) sought to reverse that by shedding a bit of light on what he described as major successes by intelligence agencies.

He called them spy stories.

Intelligence agencies learned the secrets of Iran and Libya's nuclear programs, Tenet said. They discovered the secret proliferation network of Pakistan's top nuclear scientist. And they gave diplomats the information they needed to confront North Korea about violations of international agreements.

Outside intelligence experts caution, however, that because most of what the CIA does and learns is known to only a handful of people in the U.S. government, it is difficult to fact-check Tenet's claims of success.

Tenet told a few spy stories at Georgetown University on Thursday:

— Iran: "I want to assure you of one thing: that recent Iranian admissions about their nuclear programs validate our intelligence assessments. It is flat wrong to say that we were surprised by reports from the Iranian opposition last year." Tenet wouldn't go into further detail.

— Libya: Tenet claimed the country agreed to dismantle its weapons of mass destruction (search) programs only after U.S. and British intelligence learned details of it. Intelligence agencies penetrated Libya's foreign supplier network, learned when Libya was going to receive centrifuge parts and helped stop the shipments. They also learned Libya was working with North Korea to get longer-range ballistic missiles, he said.

When negotiations began with Libya, CIA officers and British colleagues showed the Libyans how much they knew about their programs, Tenet said. "When the Libyans said they would show us their Scud-Bs, we said, 'Fine. We want to examine your longer range Scud-Cs."'

— North Korea: "It was patient analysis of difficult-to-obtain information that allowed our diplomats to confront the North Korean regime about their pursuit of a different route to a nuclear weapon that violated international agreements," Tenet said.

— Pakistan: Tenet talked about Dr. Abdul Qadeer Khan (search), the Pakistani scientist who leaked weapons technology to Iran, Libya and North Korea. Tenet said intelligence agencies are responsible for destroying Khan's "nuclear profiteering" network.

"First, we discovered the extent of Khan's hidden network. We tagged the proliferators, we detected the networks stretching across four continents offering its wares to countries like North Korea and Iran," he said.

Working with British intelligence, the agencies "pieced together the picture of the network, revealing its subsidiaries, its scientists, its front companies, its agents, its finances and manufacturing plants on three continents. Our spies penetrated the network through a series of daring operations over several years."

Critics say the United States did not put enough pressure on Pakistan to stop Khan before now.

On some topics, Tenet wouldn't bite.

Asked by a student at Georgetown about the Malaysian government's possible involvement in Khan's network, Tenet wouldn't answer. "How about baseball? Let's go there," he said.