BY JUAN O. TAMAYO

One of Fidel Castro's sons carried on an eight-month flirtation over the Internet with a person he believed was a Colombian woman. Surprise! The woman was actually a Miami man.

The trickster said the prank, broadcast on a Miami TV station, showed it's possible to get around Cuba's security.

''Guess where I am and I will make love to you without stopping,'' Antonio Castro Soto del Valle, Fidel's son and physician for the Cuban national baseball team, reportedly wrote ''Claudia'' during a January trip to Russia with his uncle Raúl.

But ''Claudia'' turned out to be Luis Domínguez, a Cuban-born Miamian who unveiled the sting on Americateve TV Channel 41 in Miami, saying it was designed to ''shatter the myth of an impenetrable'' security system.

''Claudia's'' cyber-boyfriend never revealed any state secrets and made no mention of Fidel during their more than 20 Internet chats. But he sent her what he said were his phone number and home address in Havana, wrote that he had no bodyguards and gave advance notice of a trip to Mexico -- all breaches of the tight secrecy that has always surrounded Fidel Castro's family life.

And when rumors swept Miami in mid-January that Fidel Castro had died, Domínguez said, he assured Americateve that the rumors were likely false because Antonio was keeping up his regular chats with his cyber-girlfriend.

The man who used the Canada-based e-mail address ''tonycsport@yahoo.ca'' also provided ''Claudia'' with details of a life far richer than the grind of the average Cuban -- weekends in Varadero beach, Lacoste shirts and belt buckles, a personal Apple computer and a BlackBerry with Internet access, Domínguez's files showed.

''While everyday Cubans were banned from using the Internet cafes in Havana hotels, this guy had a BlackBerry and unlimited access to the Web,'' said Domínguez, 46, a security company employee who runs a website featuring reports on Cuba's armed forces and security services -- Cubaaldescubierto.com.

Domínguez provided The Miami Herald with computer files containing chats between ''Claudia'' and ''tonycsport,'' and photos of Antonio Castro from what Domínguez said were videocam chats. Americateve producer Miguel Cossio said key details of Domínguez's tale were independently confirmed. Castro did not answer Miami Herald e-mails seeking his comments.

According to Domínguez, the sting grew out of his visit to a 2006 baseball tournament in Cartagena, Colombia, that included the Cuban team. ''Antonio was like a rock star, everyone asking to take photos with him -- and especially beautiful women,'' he recalled. ``That's where I got the idea that we could get close to him by posing as one of those women.''

First, he worked out a profile of the kind of woman the 42-year-old Castro apparently prefers. Domínguez looked at photos of Castro's current and former girlfriends, then created a ''virtual woman'' to fit the mold -- Claudia Valencia (very common names in Colombia), a 26-27 year old brunette with blond highlights and a sports journalist who, like Antonio, follows soccer and technology.

Then last summer, Claudiacartagena82@yahoo.com e-mailed ''tonycsport'' that they had met in Cartagena, and they became ''friends'' on the Tagged social networking site. Their online chats began in October, according to Domínguez.

Tonycsport sent Claudia photos of himself -- easily recognizable as Antonio Castro -- at the Beijing Olympics and in Moscow. When Tonycsport asked for photos of Claudia, Domínguez said, he e-mailed back what he would only describe as a ''virtual photo'' of Claudia. And when Tonycsport asked if she had a webcam, Claudia replied that her webcam was broken.

Some of the chats lasted just a few minutes, but the longest was for five hours, Domínguez said. And, as time passed, they grew from simply friendly to amorous.

''You know something, I want something more with you,'' Tonycsport wrote in one chat. ''I have a desire to kiss you,'' he offered in another. In a third, he wrote that he wanted to ``kiss you, love you and make love to you.''

The chats dropped off after the Cuban team was knocked out of the Baseball Classic tournament in the semifinals played in March in California.

Domínguez approached Americateve with his story about three months ago, Cossio said, and the two worked to turn it into two reports for the nightly A Mano Limpia program hosted by Oscar Haza.

''This is journalism because the BlackBerry, the computers, the travels, in any country that would be common and normal, but in the case of Cuba, he lives in a world like no other Cuban. We're showing the audience the two Cubas,'' Cossio said. ``That supposed revolutionary morality, Antonio does not live it.''

A Mano Limpia broadcast the first report on Thursday, June 4. By Saturday afternoon, when The Miami Herald first interviewed Domínguez, most of Tonycsport's several e-mail addresses had been disabled. The phone number he gave Claudia was not enabled to receive international calls.

But when Domínguez signed on to the ''Claudiacartagena82'' account on Yahoo to show The Miami Herald the record of the chats and photos, ''her'' page showed that Tonycsport was also signed on to his Yahoo.ca account.

''Wow. That can be a trap by Cuban intelligence,'' said a smiling Domínguez. "No way I am going there.''