A woman who harassed another woman in the US with "malicious" texts, phone calls, and social media posts has been sentenced to 22 months in prison.

The FBI say the posts originated from a mysterious individual, with whom the victim had no previous connection.

Law enforcement officials uncovered a trail of threats and extortion that led to a Miami college student, who is now behind bars.

"An unwanted relationship was being pushed on a victim who ultimately felt terrorized by an obsessed individual she didn't even know," said Assistant US Attorney Jodi Anton.

"The constant intimidation was destroying her life, to the point where she could barely function at work and considered suicide."

The perpetrator, Kassandra Cruz, was completing her criminal justice degree at Florida International University and spent countless hours behind the computer between her studies.

In June 2015, she became fixated on a woman she found on a pornography website and tracked down the actress through her social media accounts.

"The victim was an 18-year-old high school student at the time looking for ways to get ahead in life", said Special Agent George Nau.

"She made a bad decision trying out pornography. It was something she kept hidden from her family and employers. She didn't realise her past would come back to haunt her 15 years later."

Cruz gained access to two of the victim’s social media feeds by creating a fake persona of a male US Marine named Giovanni and sent friend requests.

The former adult film actress accepted, and Giovanni began liking and commenting on almost every picture she shared.

But the victim's suspicions began to mount in September 2015, when Giovanni started to follow and like the her friends' posts as well.

By the end of the summer, Cruz's fake profiles were blocked, which angered her.

Demands to be paid US$100,000

The FBI say she resorted to harassment and often violent threats, which were aimed not only at the victim but also her friends and family.

Included in Cruz's messages were a plot to expose the victim's hidden past making adult films - as well as demands to be paid US$100,000 (€96,073) in return for leaving the victim alone.

"Even while Cruz was being driven to jail, she still wanted to talk to the victim. She was blinded by her obsession and oblivious to the impact of her crime", Special Agent Nau added.

From the beginning of 2016 until late April, the victim received more than 900 phone calls and text messages.

Approximately the same amount of unwanted calls were made to the victim's home and work phones, before the FBI ended the stalking.

A turning point in the investigation took place in May 2016, when the FBI lured Cruz into a video chat with the victim to discuss paying the extortion demand.

An in-person meeting was arranged during the chat that allowed agents to finally make an arrest.

In August 2016, Cruz was sentenced to 22 months in prison after having been found guilty of cyberstalking.