They call themselves unwitting tourists, international students, and entrepreneurs.

But is something more nefarious at work?

Could there be spies in our backyard, right here in South Florida?

In just 18 months, authorities have arrested and charged six Chinese nationals in five separate incidents from Palm Beach down to Key West.

WPTV broke the story of Yujing Zhang last April, after she was charged with trespassing at President Donald Trump's Mar-a-Lago club and lying to the Secret Service.

Zhang wasn't the only recent case in South Florida.

In Sept. 2018, authorities arrested Zhao Qianli for taking photos at a Naval base in Key West.

In Dec. 2019, Palm Beach Police arrested 56-year old Lu Jing for trespassing at Mar-a-Lago and resisting arrest without violence.

Later that month, on the day after Christmas, 27-year old Lyuyou Liao allegedly snuck into Naval Air Station Key West and was photographing the base.

Then on Jan. 4, both Yuhao Wang and Jielun Zhang were arrested at the same Navy base in Key West for the same crime: photographing defense installations.

The string of arrests garnered international attention and raised the question: why here?

Former CIA analyst Lisa Ruth, who now works as President and CEO of CTC International Group, told WPTV Florida is a "target-rich environment."

"You start with Mar-a-Lago, [which] is absolutely an intelligence target for everybody around the world," said Ruth.

THE WINTER WHITE HOUSE

Despite being a point of interest for nations across the globe, only two foreign nationals, both Chinese, have been arrested in the last year at President Trump's club on Palm Beach.

The first was Yujing Zhang. Her case garnered international attention, both for the details of her arrest and Zhang's erratic behavior in court.

When the Secret Service detained Zhang at Mar-a-Lago, they said they found four cellphones, a laptop, a hard drive and a thumb drive.

Law enforcement also found a device in Zhang's hotel room that could detect hidden cameras, as well as $8,000 in U.S. and Chinese currency, nine USB drives, five USB cards, and several credit cards in her name.

"What you have is a lot of entrepreneurs untrained who are trying to collect specific information," said Nicholas Eftimiades in an Skype interview. Eftimiades is a former intelligence officer and the author of 'Chinese Intelligence Operations.'

Prosecutors never filed any espionage-related charges against Zhang. Instead, she was charged with trespassing and lying to a federal agent. At a bail hearing in April, a federal judge commented from the bench that it appeared "Ms. Zhang was up to something nefarious."

Zhang's bizarre behavior throughout the court proceedings also drew scrutiny. She opted to fire her public defender and represent herself at trial, and the judge overseeing her case accused her of "playing games with the court" more than once.

A jury found Zhang guilty on both charges. She was sentenced last November to eight months in prison with time served and is currently awaiting deportation at the Glades County Detention Center.

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Weeks after Zhang's sentencing, Palm Beach Police arrested 56-year old Lu Jing for trespassing at Mar-a-Lago and resisting arrest without violence.

Authorities said Jing was told to leave Mar-a-Lago property, but she snuck back in a through a service driveway and was spotted taking photos inside the club. She fled on foot and was detained nearby, police said. Jing's trial will begin next week.

Much like Zhang, prosecutors have not charged Jing with any espionage-related counts. Jing faces two misdemeanors for trespassing and resisting arrest without violence.

Despite both Zhang and Jing not facing any sort of espionage-related charges, WPTV spoke with former intelligence operatives who believe something was amiss.

"The entire thing is concerning," said former Secret Service Agent Tim Miller, who now works for LionHeart International Services Group. "It's troubling that there have been a number of incidents involving Chinese nationals. They [could be] trying to identify what cameras see at certain times. It's not just about intercepted communications. It can be situational awareness."

Those caught tend to deploy the same defense: claiming they are just tourists, students, or entrepreneurs drawn to certain Florida locations.

Lisa Ruth thinks it's "all one in the same."

"I think the bumbling tourist is the amateur spy, and keep in mind the spy moniker doesn’t mean someone who is trained by an intelligence person," said Ruth. "That means somebody who an intelligence officer is directing to go do something."

The fascination doesn't end with Mar-a-Lago.

SNAPPING PHOTOS IN THE KEYS

Since Sept. 2018, authorities have charged Zhao Qianli, Lyuyou Liao, Yuhao Wang, and Jielun Zhang under the espionage act, for photographing and sketching defense installations. All four are accused of taking photos at Naval Air Station in Key West.

Zhao Qianli pled guilty and a judge sentenced him to one year in prison, the maximum sentence he could hand down for the offense. Qianli was in the United States on an expired student visa.

"What you find in Chinese intelligence operations as a whole is that they incorporate a whole of society approach," said Eftimiades. "It's not just trained intelligence officers recruiting people and targeting things as we see normally."

The second case is against Liao, who is facing charges for an incident on Dec. 26, 2019.

The criminal complaint alleges Liao did the same as Qianli, walked around a perimeter fence, and entered the restricted military base. Liao claimed he was taking photos of the sunrise that morning after Christmas day, but investigators found photos of the base on his camera.

Liao's attorney said his client never intended to trespass. He's pled not guilty in the case.

Less than 10 days later, authorities arrested both Yuhao Wang and Jielun Zhang for taking photos inside the Navy base in Key West. They didn't sneak onto the base in the dead of night or try and conceal themselves in any way.

Instead, the two just drove right in.

"It's a pretty simplistic and amateur approach which you find a lot in Chinese collection efforts," Eftimiades told WPTV.

According to the criminal complaint, Wang and Zhang drove to a guard station at the entrance, but a guard told them to turn around because the two did not have proper identification.

Instead, the criminal complaint alleges they ignored the directive and drove into the base, spending several minutes inside before being detained. Court records show both admitted to taking photos of the base. Both defendant's have pled not guilty to their charges.

SEE CASE EXHIBITS AGAINST YUHAO WANG AND JIELUN ZHANG HERE

Eftimiades has tracked federal cases involving Chinese citizens nationwide over the last 20 years. His research shows 20 federal cases in Florida in the previous two decades.

Of those, four incidents involving five Chinese nationals have occurred here in South Florida in just the past 18 months. That figure does not include Lu Jing, who faces charges in state court.

Experts WPTV spoke with said Chinese espionage can be beneficial, not just for intelligence gathering, but economically as well.

There is a "close relationship between private enterprise and government," Ruth told WPTV.

Eftimiades concurred, noting that "the Chinese government sets in doctrine at the highest level, and then it filters down through state-owned enterprises, through companies."

Former intelligence officials say the end game is well known.

"Their plans as [President Xi] Jinping has said many times, for China to ascend to its rightful place at the top of the world," said Eftimiades. "This is all about growth development, military and economic. We have a legal system in place, a rule of law that discourages and punishes these acts, but they don’t."