Australian swimmer Shayna Jack in scary extortion attempt

Aussie swimmer Shayna Jack. Photo / Getty

Australian swimmer Shayna Jack's lawyer believes her case to avoid a four-year ban for alleged banned substance use has been prejudiced by a vicious extortion attempt.

Jack has reported communication from an unknown overseas hacker to Queensland Police and the Court of Arbitration of Sport.

More than six messages have reportedly been sent to the 21-year-old's Facebook page since Monday, before her account was hacked in the early hours of Tuesday morning, the Daily Telegraph reports.

The hackers first messaged Jack via Facebook, stating they were going to post photos of her unrelated to her anti-doping matter unless she pays.

Jack informed Queensland Police on Monday while she also immediately employed an IT specialist to help secure her personal details. She has also deleted her Instagram account.

Shayna Jack at the 2018 Commonwealth Games. Photo / Photosport

On Monday night, at around 9.40pm, Jack received another message that read: "I'm in a different country, you can't do anything against me, you have to pay." I can see what you're doing at all times.''

Jack failed to respond after being advised not to communicate with the hackers. Another message arrived at 3am on Tuesday morning which read: "I will share something that will disturb you, if you do not answer.''

Jack again failed to respond and then only a few hours later the hackers posted on her Facebook account: "I regret I used doping in the 2017 Olympics.''

The post led to Jack's lawyer, Tim Fuller, to claim: "In our opinion, this prejudices her case, to a certain extent.

"Even though it's not with the court, in the court of public opinion it doesn't help does it?

"She's very upset. It's disgraceful.''

Jack was required to inform the sports arbitrator of any development that could lead to major ramifications to her appeal.

She tested positive to the banned substance Ligandrol before last year's World Swimming Championships in South Korea.