A Melbourne dentist who claims he was defamed in an anonymous online review has convinced a Federal Court judge to order technology giant Google to unmask the disgruntled customer so he can launch "groundbreaking" legal action.

Key points: Dr Matthew Kabbabe claims the review has cost him a significant amount of money

Dr Matthew Kabbabe claims the review has cost him a significant amount of money Historically, attempts to convince Google to unmask anonymous internet users have taken months because of red tape related to an international treaty

Historically, attempts to convince Google to unmask anonymous internet users have taken months because of red tape related to an international treaty Mr Kabbabe's lawyer has convinced a judge to allow him to use a loophole that will circumvent the treaty by serving Google via registered international mail

Matthew Kabbabe said the single negative review, lodged on Google about three months ago, had had a profound impact on his teeth-whitening business and his life.

"I believe it is extremely unfair that people are allowed to anonymously attack honest, hardworking small businesses," Dr Kabbabe told the ABC.

The review in question, authored by a user called "CBsm 23", is the only one containing negative comments on Dr Kabbabe's business page. The rest of his reviews have five stars.

He has been unsuccessful in getting Google to take down the review.

His lawyer, Mark Stanarevic from Matrix Legal, described the decision by the Federal Court as "groundbreaking".

"A bad review can shut down a business these days because most people live and breathe online," Mr Stanarevic said.

"Sometimes people just look at one or two bad reviews and decide to go somewhere else.

"We think Google has a duty of care to Australian small businesses and businesses globally for allowing these reviews to go on.

"Google has to be accountable for these actions."

Google compelled to unmask 'CBsm 23'

The order by Justice Bernard Murphy compels Google to turn over identifying information of "CBsm 23", including any names, phone numbers, IP addresses and location metadata.

The technology giant has also been ordered to provide any other Google accounts, including full name and email addresses, which may have originated from the same IP address during the same period of time.

Lawyer Mark Stanarevic said Google had a duty of care to reveal the authors of bad reviews published by the internet giant. ( Unsplash: Paweł Czerwiński )

The orders in question will today be mailed to Google, which is located in Mountain View, California, by international registered post.

Any information garnered from Google will then be used to sue the writer of the review.

"We want to know who the anonymous reviewer is. They've defamed my client. He's lost thousands and thousands of dollars," Mr Stanarevic said.

"It's cost him a lot of money and he hasn't been coping very well with it.

"It's been totally unjust."

And Mr Stanarevic said he was exploring the prospect of more legal action.

"Right now people are hiding behind the veneer of anonymity," Mr Stanarevic said.

"I've had a number of business owners over the years who have lost their livelihoods because of antagonistic and defamatory reviews on Google and I've been instructed to look at even potentially assessing a class action."

Lawyer Mark Stanarevic says a Federal Court judge's decision to force Google to unmask the author of a bad review is "groundbreaking". ( ABC News: Danny Tran )

How to reveal an anonymous reviewer

Ordinarily, serving an international company like Google would take several months because, under an international treaty known as the Hague Service Convention, the documents would first have to be lodged and processed in two countries.

First, the order would have to be lodged with a central authority in Australia.

A request would then have to be made with a central authority in the United States, which would then organise for it to be served.

The legal decision is significant because Mr Stanarevic has found a legal loophole which allows Google to be served directly by international registered post.

"This can essentially speed up the process in terms of people seeking justice and resolution," he said.

Mr Stanarevic expects Google to comply with the order because the United States is a party to the Hague Convention.

"We don't think they'll fight it," he said. "We think common sense will prevail."

He said he was expecting a response in a few weeks, but in the meantime he had a message for the denizens of the internet.

"If you're out there trying to hide by anonymity, even via VPN, I think the court system's catching up now and there are ways and means of obtaining that information," he said.

A spokeswoman for Google said the company does not comment on ongoing legal matters.