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Just days before the attacks of September 11, 2001 one ranking U.S. military intelligence officer was recruiting linguists for counter-drug operations -- when he received a phone call from a woman claiming that one of his potential hires had ties to terrorism.

They agreed to meet in a downtown Manhattan bar so the officer, who still works in the security sector and requested not to be named, could take down the details of the tip.

"In walked an absolutely stunning, drop-dead gorgeous woman," he recalled. "We just had a casual conversation. She mentioned she had family in Florida – they happened to be right where I was living."

A coincidence? 

The notion of "honey trap" spies was thrust into the limelight this week after it was revealed by Axios that Rep. Eric Swalwell (D-Calif.) was seemingly ensnared by a woman suspected of being a Chinese espionage operative named Christine Fang or Fang Fang.  She helped raise money for his 2014 congressional re-election campaign and recruited at least one intern in his office.  However, U.S. investigators in the northern California Bay Area believe Fang was also circling close to numerous up-and-coming politicians between 2011 and 2015, engaging in sexual relationships with at least two mayors in other states.

CHINA'S EXTENSIVE 'HONEY TRAP' SPY NETWORK COULD INVOLVE THOUSANDS OF PLOYS UNDERWAY NOW, EX-OPERATIVE SAYS

In this case, years earlier, the U.S. officer – who was around 40 at the time and has since retired – flew off to Eastern Europe just before Al-Qaeda terrorists slammed two commercial jets into New York's "Twin Towers."  When he returned, his role was re-positioned into the urgent realm of counterterrorism.  Soon he started to train other military and intelligence authorities for things like spotting spies and identifying honey trap techniques. Little did he know that he had slipped into one himself.

"We started dating, but it was very slow and for me not a very serious relationship," he explained. "One day, there would be a toothbrush left at my place; the next week, it was something else. It was very slow, which is why these operations are so effective."

TOPSHOT - A protester holds a US flag outside of the Chinese consulate in Houston on July 24, 2020, after the US State Department ordered China to close the consulate. - The US ordered China to close its Houston consulate, Beijing said on July 22, in what it called a "political provocation" that will further harm diplomatic relations. (Photo by Mark Felix / AFP) (Photo by MARK FELIX/AFP /AFP via Getty Images)

The officer, who traveled a lot for work himself, noted that he really knew very little about his "girlfriend." She claimed to be of Eastern European descent but was an American. She didn't really work, but said she had a trust fund, traveled around a lot and occasionally did consulting work. She was supposedly educated in the U.S. but capitalized her words and had other grammatical habits not common to the U.S. system.

And while the concentration this week – given the Swalwell scenario – has been on its use by the Chinese government, U.S. intelligence officials say it happens far and wide and by a multitude of countries.

"She had a U.S passport," the officer said. "But my neighbor at the time learned she had other passports too."

And it was the neighbor who alerted him to the many nights that his office light was on while he was out of town, indicating she was on his computer and shuffling around through the drawers. The number of unsettling "offs" on the checklist just kept growing.

"She even faked a pregnancy – I thought it was strange, as a father already, that her stomach had been growing a little bit but nothing else. I later learned she was getting collagen shots in her abdomen to get that little pooch," the officer continued.

But it was when his "girlfriend" started asking questions about the cinderblock the house was made from and was it possible for someone to shoot through the roof that he had his own "ah-ha" moment and a feeling of dread washed over.

SWALWELL REFUSES TO EXPLAIN RELATIONSHIP WITH SUSPECTED CHINESE SPY ACCUSED OF AFFAIRS WITH MAYORS

It was a Friday night, and she wasn't home. As he dug around, he found copies of his top security clearance tucked into the folds of a Shape magazine where she assumed he would not find it. The intel officer also discovered a gate pass to MacDill Air Force base, even though she had no known reason for ever going there.

Immediately, the officer said, he alerted superiors and federal investigators conducted a sweep of the house to check for any surveillance. But the unsettling feeling only stung further given that the apparent spy had managed to establish domicile under Florida law, which required the extra layers of needing to be served with an eviction notice and a changing of the locks.

"I found myself doing counterterrorism detection routes going to and from the house and making sure I wasn't being followed, the sort of thing I was tasked with doing in Afghanistan," the officer recalled. "It just consumes you."

Representative Eric Swalwell, a Democrat from California, listens during a House Judiciary Committee hearing in Washington, D.C., U.S., on Wednesday, June 24, 2020. Photographer: Anna Moneymaker/The New York Times/Bloomberg via Getty Images

According to the officer, he filed an FBI Freedom of Information Act (FOIA) request years later to try and determine what happened – but the request was denied, as it remained an "open investigation."

Based on his own research, the officer believes the honey trap was set by a former U.S. Air Force serviceman linked to a foreign "Liberation Army," who recruited the young woman to gather as much compromising information as possible on those in the U.S. who were involved in countering their mission.

"I was one of the lucky ones, she didn't have anything on me, and there was no way I would betray my country for anything," the officer surmised. "But others aren't always so lucky."

"The honey trap is one of the most commonly used techniques for intel gathering or gaining leverage or blackmail. Since prostitution is widely known as the oldest profession, the honey trap is one of the oldest intelligence-gathering techniques," said Tony Schiena, Chairman of security firm MOSAIC. "It continues to be an effective technique as it's extremely difficult to prevent."

Department of Justice sign, Washington DC, USA. Many law enforcement agencies are administered by the DOJ, including the FBI, DEA and Federal Bureau of Prisons

According to background research conducted on both the "honey trap" operative and the alleged handler in this case, they were never indicted, and both are listed as residing in the United States. Their current means of employment remain unclear.

"One of the most important things is awareness and education," the retired intel officer added. "Men – and women – are willing to overlook a lot when things are good in the bedroom."