Hunting spies is difficult, but Cuban spies are notoriously hard to detect, former senior intelligence officials said a day after an American husband and wife were indicted on charges of spying for Cuba.
Walter Kendall Myers and his wife Gwendolyn of Washington were arrested on Thursday after a three-year investigation that began before Myers' retirement from the State Department in 2007. They had been spying for Havana for 30 years, according to the US government.
Investigations like this typically take years to come together because they usually turn on small pieces of information, and Cuban spies often leave few traces.
Cuban intelligence specializes in recruiting "true believers" rather than agents who are out to make money, these officials said. They spoke on condition of anonymity because the investigation is ongoing.
Myers appears to be one of the true believers. He praised Castro in a personal journal he wrote in 1978 as a "brilliant and charismatic leader" who is "one of the great political leaders of our time."
And he called the United States government "exploiters" who regularly murdered Cuban revolutionary leaders.
Castro called the case of two Americans accused of spying for Cuba "strange" on Saturday and questioned whether the timing of their arrests was politically motivated.
"Doesn't the story of Cuban spying seem really ridiculous to everyone?" Castro asked, without commenting on its validity.
Castro said he doesn't recall meeting them when he was still president.
"I met during this time with thousands of Americans for various reasons, individually or in groups, on occasion with gatherings of several hundred of them," said the 82-year-old, who ceded power to his brother Raul when he fell ill nearly three years ago and has not been seen in public since.
Politically motivated spies don't leave a money trail or engage in conspicuous consumption that might attract attention, a common way spies are first identified.
The former officials said the Cuban intelligence service is willing to wait years, even decades, for a recruit to work him or herself into a useful position.
Cuba is content to have midlevel officials who have access to information but no policymaking power. For these reasons, Cuban agents are notoriously difficult to detect unless a pattern of unusual inquiries eventually attracts attention, they said.
According to court documents, Myers had been put on a watch list by his State Department boss in 1995, meaning he was under suspicion. The FBI investigation didn't start until 2006, after his boss raised fresh suspicions when he returned from a trip to China.
In his last year alone at the State Department, Myers accessed over 200 sensitive documents related to Cuba, according to court documents.
Secretary of State Hillary Rodham Clinton has ordered a damage assessment of what the couple may have revealed.
David Kris, assistant attorney general for national security, described the couple's alleged spying for the communist government as "incredibly serious."
A formal assessment of the damage the pair may have caused will likely not begin until after a trial, or if the two disclose the information they passed as part of a plea agreement, said one former senior US intelligence official. But already individual US intelligence agencies are scrambling to figure out whether US spies in Cuba or elsewhere were identified by the pair.
The government-wide assessment is expected to be headed by National Counterintelligence Executive Joel F. Brenner.
Obama administration officials say Kendall Myers had access to highly sensitive material while working for the State Department's intelligence arm, which receives intelligence reports from all agencies.
"Given where he worked, his value to the Cubans would be both in terms of 'gossip' about US officials - who is being assigned to Cuba, what White House officials are asking for info, etc. - and, of course the raw data that comes across his desk," said Amb. Dennis Hays, the State Department's Coordinator for Cuban Affairs from 1993 to 1995.
Hays said because Myers didn't directly work on Cuban issues he didn't have the same opportunities to affect US policy on Cuba that Ana Montes did, the senior Cuban spy convicted by the United States in 2002.
But someone with top secret clearance can do a lot of damage because he would have had broad access to intelligence material and a license to search for what he wanted, said the former senior intelligence official.
One key question to be answered will be whether the Cubans were using Myers to produce information for other countries, like Russia, Venezuela, Iran or China.
Like Montes - whom he admired - Myers memorized most of the information he passed to his Cuban handlers rather than take classified documents home, an effort to avoid detection.
He did hide some papers in bookends at his house, holding onto them for no longer than a day, according to court documents unsealed on Friday.
Myers received his orders by Morse code, and he and his wife usually hand-delivered intelligence, sometimes in the grocery store. Myers was familiar with spy tradecraft, like using water-soluble paper to take notes, according to court documents.
Chris Simmons, a former counterintelligence officer with the Defense Intelligence Agency who worked on the Montes case, said Myers' role as an instructor at the Foreign Service Institute posed a real threat because he would be able to provide dossiers and personal observations on his students to the Cuban government.
The institute trains officers in regional specialties from all corners of the US government, not just the State Department. When those students go abroad for State, the US military, or undercover as CIA officers, foreign intelligence services may already have files on them to attempt recruitment.
It was at the institute that Myers first met the Cuban official who recruited him into spying in 1978.
The former intelligence officer who worked on spy cases said Myer's would be valuable to the Cuban government for his ability to spot potential recruits among the students.
Myers could also have provided leads and files on students from the prestigious Johns Hopkins School of Advanced International Studies in Washington.
Myers has been an adjunct professor there since the late 1980s, said Felisa Neuringer Klubes, a spokeswoman for the school. He taught most recently this spring semester. Many US government employees get advanced degrees there or go on to teach there. It is where Myers earned his doctorate.
Myers usually taught British politics and general international relations. His expertise is European studies, specifically Britain, said Klubes. He is one of at least 130 adjunct professors at the school at any given academic year, she said.
Mitchell Orenstein, an associate professor of European studies, has known Myers for about two years and said he was surprised at the charges.
"He's been a fantastic colleague, a great guy," Orenstein said. "He was in a happy retirement and planning on doing some sailing with his wife."
In fact, Myers and his wife told the undercover FBI agent that they had been planning to sail to Cuba and live on their boat. They considered Cuba their home, though they had only visited it.
Orenstein said he never heard Myers talk about Latin American relations. He didn't hear him mention Fidel Castro or speak about American politics.
He said Myers was "a smart person who we thought had done a good job at the State Department."
"The students love him," he said.
An undercover FBI agent posing as a Cuban handler approached Myers outside Johns Hopkins on April 15, according to a law enforcement official speaking on a condition of anonymity about the ongoing investigation. That began a series of meetings that resulted in the couple's indictment this week.
