Fraudsters used iSpoof to disguise their phone numbers then posed as representatives of legitimate British banks, including Barclays, Santander, HSBC, Lloyds, Halifax, First Direct, Nationwide and TSB, police said.
In their effort to identify and prosecute the fraudsters, police allowed iSpoof to continue operating so they could infiltrate the site and gather information on its users.
The website was created in December of 2020 and had 59,000 user accounts, police said. Of 10 million fraudulent calls made through iSpoof, 40% were to numbers in the United States and 35% were in the U.K.
Because of the large number of potential suspects, police are focusing first on U.K. users who paid at least 100 pounds in Bitcoin to use iSpoof.
The suspected organizer of the website was arrested earlier this month in East London. He has been charged with a number of offenses and remains in custody, police said.
British authorities have forwarded information about other suspects to law enforcement agencies in The Netherlands, Australia, France and Ireland.