Peter Bergen is CNN's national security analyst, a vice president at New America and a professor at Arizona State University. He is the author of " United States of Jihad: Investigating America's Homegrown Terrorists ."

(CNN) President-elect Donald Trump says that he doesn't believe the US intelligence community's assessment that the hack of the Democratic National Committee (DNC) was the work of the Russians. To bolster his point, Trump cites the CIA's faulty intelligence about Saddam Hussein's supposed weapons of mass destruction in the run-up to the invasion of Iraq in March 2003.

In a statement about the CIA that he issued late last month, Trump said, "These are the same people who said Saddam Hussein has weapons of mass destruction." On Sunday at his Mar-a-Lago estate, Trump made this point again to reporters, saying, "if you look at the weapons of mass destruction, that was a disaster and they were wrong."

But there are some significant differences between the CIA's weapons of mass destruction fiasco 14 years ago and the evidence that is now being offered by the American intelligence community about the Russian hacking.

The WMD fiasco did much to harm the standing of the George W. Bush administration and its key figures, such as Secretary of State Colin Powell, who famously made the case for the impending Iraq War to the United Nations. The war resulted in hundreds of thousands of deaths, trillions in wasted US spending, and fomented chaos that continues in the Middle East. It was such a black eye for US intelligence that large changes were made to the process of making intelligence assessments.

'Curveball'

The faulty assumption that Saddam Hussein was reconstituting his weapons of mass destruction program rested, in part, on intelligence sources who were lying. One of them was an Iraqi defector with the telling alias of "Curveball," who claimed that Hussein possessed mobile bioweapons labs.

This became a central exhibit in the George W. Bush administration's assertions that Hussein had a biological weapons program. But Curveball later admitted he had made up the whole story.

A month before the March 2003 invasion of Iraq, CIA Director George Tenet testified before the Senate Armed Services Committee that Iraq had "provided training in poisons and gases to two al Qaeda associates." But what Tenet didn't know was that this information had come from a militant who had been tortured in Egypt.

In December 2001, Ibn al-Shaykh al-Libi, a Libyan militant affiliated with al Qaeda, was captured in Pakistan. The CIA then "rendered" Libi to Egypt. Once in Egypt's grim prisons, to improve his chances of better treatment, Libi fed his interrogators a number of fairy tales, including that Osama bin Laden had sent two operatives to Iraq to learn about biological and chemical weapons.

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Because Libi's story encapsulated the key arguments for the Iraq War, his tale was picked up by President Bush in a keynote speech in Cincinnati on October 7, 2002, in which Bush laid out his rationale for the coming war with Iraq, saying, "We've learned that Iraq has trained al Qaeda members in bomb-making and poisons and deadly gases."

But once he was back in American custody, on February 14, 2004, Libi recanted what he had falsely told his Egyptian jailors. Libi told his US interrogators that he had "fabricated" his tale of the Saddam Hussein-al Qaeda-poison connection to the Egyptians following "physical abuse and threats of torture."

Learning from mistakes

The intelligence community was determined to learn from these costly mistakes and instituted more "alternative analysis" and Red Teams to challenge its conclusions. CIA Director John Brennan made essentially the same point this week in an interview with PBS' Judy Woodruff: "A number of steps ... were taken to make sure that we're going to be as accurate as possible, so it's been light years since that Iraq WMD report."

The WMD fiasco, which was probably the most damaging episode for the credibility of the CIA in decades, made the agency much more careful about its handling of circumstantial evidence, as was the case during the hunt for Osama bin Laden.

Throughout the search for bin Laden there was never any definitive evidence that al Qaeda's leader was in fact hiding in the compound in Abbottabad, Pakistan, where he was eventually killed by US Navy SEALs on May 2, 2011.

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The CIA's hunt for bin Laden heated up in the summer of 2010 with the discovery of a possible bin Laden courier living in Pakistan who was known as "the Kuwaiti."

As I learned while I was reporting my book "Manhunt," which detailed the long search for bin Laden, the small cadre of analysts at the CIA who were aware of the intelligence on "the Kuwaiti" subjected it to a formal process of structured analytical techniques, drilling down on key questions: What's the body of evidence that the Kuwaiti is bin Laden's courier? Who else could the Kuwaiti be if he weren't the courier for al Qaeda's leader? Was the Kuwaiti even still working for al Qaeda?

Cognizant of the lessons of the WMD fiasco, an intelligence official told me that dissent was actively encouraged among the analysts leading the hunt for bin Laden. "We kept explaining to our group: 'If you see something that doesn't make sense, you need to raise your hand now.'"

Digital fingerprints

The evidence in the Russian hacking case, however, is not the kind of circumstantial case that the CIA built during the hunt for bin Laden and is based instead on " digital fingerprints " that point to Russian involvement.

The FBI and Department of Homeland Security took the unusual step last week of releasing publicly an account of the Russian hacking efforts (codenamed by the US government GRIZZLY STEPPE), which goes into considerable detail about how and when the hacking was accomplished.

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The report portrays a sophisticated set of spear-phishing campaigns that began in the spring of 2015. The report says that spear-phishing emails "tricked recipients into changing their passwords" and through the harvesting of those credentials the Russians were "able to gain access and steal content, likely leading to the exfiltration of information from multiple senior party members."

Interested readers can find the report here.

This week Trump will hear directly from top US intelligence officials about their evidence and reasoning for pointing to Russia as the source of the DNC hacking. If Trump is to retain credibility with the intelligence professionals who soon will be working for him, he should be listening carefully to what they have to say rather than dismissively invoking the CIA's failures in the run-up to the Iraq War.