Three major Covid-19 vaccines are being advertised for sale on the darknet – the part of the internet not visible to search engines and which requires specialised software to access, an analysis of 15 marketplaces has found.

Researchers at the global security company Kaspersky found advertisements for the Pfizer, AstraZeneca and Moderna vaccines, as well as sellers advertising unverified vaccines.

The majority of sellers came from France, Germany, the UK and the US, and prices per dose ranged from A$250 to $1,200, with an average cost about $500.

“Communications are made via encrypted messaging apps like Wickr and Telegram, while payments are requested in the form of cryptocurrency, primarily bitcoin,” the analysis found.

“The majority of these underground sellers have made between 100-500 transactions, indicating that they’ve been completing sales but what exactly darknet users are purchasing remains unclear. With the information available to Kaspersky experts, it’s impossible to tell how many of the vaccines doses being advertised online are actual doses and how many advertisements are a scam.”

An Australian National University regulation and global governance researcher, Prof Roderic Broadhurst, and his colleagues conducted a similar darkweb analysis in April, examining personal protective equipment and novel Covid-19 “treatments” being sold on 20 darknet marketplaces.

That study found 12 markets posting Covid-19 products, with three markets accounting for 85% of all 645 listings. Even at that time, before any strong vaccine candidate had been produced, Broadhurst found sellers advertising vaccines, the most expensive of which was listed at A$24,598. Vaccines allegedly sourced from China were also costly, at $23,000.

Broadhurst said that the majority of vaccines on the darknet were likely to be scams, with no vaccine actually on offer, or vials being sold which actually contained saline solution – a mixture of sodium chloride in water. He said many positive reviews on the listings from these sellers were repeated across multiple sellers, and were also likely to be fake. Many vendors were trying to scam people to collect personal information.

“Most people are just going to lose their money and be scammed,” Broadhurst said.

“But the reality is, there will be some genuine delivery of product among the fake advertisements. It can’t be ruled out, as a very small number of sellers have supply chain connections, or access to leftover product or product that fell off the back of a truck.”

Dmitry Galov, a security expert at Kaspersky, said it was not surprising sellers were trying to capitalise on the vaccination campaign.

“Over the past year, there have been a whole host of scams exploiting the Covid topic, and many of them have been successful,” Broadhurst said. “Right now, not only are people selling vaccine doses, but they’re also selling vaccination records – pieces of paper that can help you travel freely. It’s important for users to be cautious of any ‘deal’ related to the pandemic, and, of course, it’s never a good idea to buy a vaccine off the darknet.”

Australia’s drug regulator, the Therapeutic Goods Administration, said vaccines bought online were likely to be unsafe and ineffective.

“These vaccines could also be counterfeit,” the administration said. “People or websites claiming to sell a Covid-19 vaccine may not deliver any product, and they may instead steal your money or your personal information.

“Scammers may create websites, advertise through social media or use SMS messages that look genuine. Always verify the information by checking an independent or trusted source.”