Police say four Chinese nationals living in Sydney used dating sites, job ads and messaging apps to swindle at least $US100 million ($148 million) from people around the world.
It is alleged the group set up businesses and bank accounts in Australia to launder money obtained through the "sophisticated" investment scam.
The men, who are allegedly part of a criminal syndicate, are accused of manipulating victims to gain their trust before offering investment opportunities.
Victims were allegedly directed to a mix of fraudulent and legitimate online trading platforms, dealing in foreign exchange and cryptocurrencies, which were altered to show phoney positive returns.
Most of the alleged victims are based in the US, with the Australian Federal Police's (AFP) cyber security team leading the joint investigation after a tip-off from the United States Secret Service in August.
AFP officers swooped on four men over two separate raids in October and November.
Two men, both aged 19, were arrested in Pyrmont on October 20, and were charged with recklessly dealing with the proceeds of crime.
On November 24, officers arrested another two men alleged to be the "controllers" of the group at Sydney and Melbourne airports respectively.
It is alleged the men, aged 24 and 27, had bought one-way flights to Hong Kong set to depart on the day of their arrests.
They have been charged with dealing in proceeds of crime in money or property worth $10 million or more.
The two men arrested in November have been remanded in custody to re-appear before Downing Centre Court on January 18, 2023.
The two 19-year-olds will next appear in the same court January 19, 2023.
The investigation — codenamed Operation Wickham — was conducted alongside a NSW Police probe.
It is alleged the AFP has restrained $22.5 million from 24 bank accounts linked to the syndicate.
Investigators are yet to ascertain the full scope of alleged fraud committed against Australian investors.
Analysis of the group's alleged activities has identified $US100 million in losses based on victims reports.
AFP Cybercrime Operations Eastern Command Detective Sergeant Salam Zreika said more people were falling victim to cyber scams every day and, with some losing their life savings.
"It is essential people exercise the utmost caution if cold-approached online or on the phone by people trying to sell financial or investment services. Criminals are ruthless and will stop at nothing to take your money," she said.
"Refrain from investing in foreign exchange, crypto-currency or speculative investments with people you've only ever encountered in the online environment. If you are unsure, get a second opinion from a professional, in-person."
Detective Superintendent Martin Fileman, from NSW Police's Sydney city command, warned that if something "sounds too good to be true, it probably is".
