CNN  — 

Ana Montes, an American citizen convicted of spying for Cuba, has been released from US federal prison in Fort Worth, Texas, according to Federal Bureau of Prison online records.

Cuba recruited Montes for spying in the 1980s and she was employed by the Pentagon’s Defense Intelligence Agency as an analyst from 1985-2001. She was eventually promoted to be the DIA’s top Cuba analyst.

The FBI and DIA began investigating her in the fall of 2000 but, in response to the September 11, 2001 terror attacks, she had access to plans for US attacks against Afghanistan and the Taliban.

On September 21, 2001, Montes was arrested in Washington, DC, and charged with conspiracy to deliver defense information to Cuba.

In early 2002, she was sentenced to 25 years in prison after pleading guilty to espionage. The judge who sentenced Montes ordered her to be supervised on release from prison for five years.

Regarding Montes’ release, Florida Sen. Marco Rubio slammed Montes for betraying the US and assisting Cuba’s communist regime.

“Americans should remember Ana Belén Montes for who she really is, despite the fact that she has served her time in prison. If we forget this spy’s story, it will surely repeat itself,” Rubio said in a statement released on Saturday.

Ana Montes, now 65, was known as the Queen of Cuba, an American who for over a decade and a half handed over so many US military secrets to Havana that experts say the US may never know the full extent of the damage.

In 1984, Montes was working a clerical job at the Justice Department in Washington and studying for a master’s degree at Johns Hopkins University.

She often found herself railing against President Ronald Reagan’s support for rebels fighting pro-communist regimes in Central America.

“She felt that the US didn’t have the right to impose its will on other countries,” said FBI Special Agent Pete Lapp, the man who eventually led the investigation against Montes, and ultimately arrested her.

Her anger about US foreign policy complicated her relationships and drew the attention of Cubans who enticed her to turn her back on friends, family and her own country.

Someone at Johns Hopkins noticed Montes’ passionate views about Cuba and soon she was introduced to recruiters, and agreed to help the Cuban cause.

At about the same time, Montes applied for a job at the Defense Intelligence Agency, where workers handle US military secrets on a daily basis. When she started there in 1985, the FBI says she was already a fully recruited Cuban spy.

One night in 1996, Montes was called to consult at the Pentagon during an ongoing international incident, but she broke protocol by failing to remain on duty until dismissed. This raised suspicion.

Four years later, DIA counterintelligence officer Scott Carmichael heard the FBI was looking for a mole – an unidentified spy inside the DIA who was working for Cuba.

The suspect had traveled to the US Naval Base at Guantanamo Bay, Cuba, at a specific time. When he looked up a list of DIA employees who visited Gitmo during those dates, a familiar name popped up – Ana Montes.

“The moment I saw her name, I knew,” Carmichael said.

After that, Carmichael and FBI agent Lapp teamed up to prove that the DIA’s Queen of Cuba was really a spy.

Thanks to “very sensitive” intelligence, it was known that the unidentified DIA mole had bought a specific brand, make and model of computer at a specific time in 1996 from an unknown store in Alexandria, Virginia.

Lapp was able to find the store’s original record that linked that computer to Montes, confirming their beliefs.

CNN’s Thom Patterson contributed reporting.