US authorities have charged 37 Russians and Eastern Europeans with using US bank accounts to launder money from hacked accounts.
This follows the arrest by UK police of 19 people connected with the theft of millions of pounds from British bank accounts.
Police officers from several UK police forces raided addresses in London to arrest 15 men and four women aged between 23 and 47.
Those arrested allegedly used the Zeus Trojan software to steal log-ins and personal banking details to draw money from accounts.
Police estimate the criminals stole £6m from UK banks and nearly £2m from US banks.
Dozens of suspects have been arrested on both sides of the Atlantic, with more charges and arrests expected, according to US reports.
Police said the gang specialised in sending e-mail messages containing links to the Zeus Trojan malware to specifically targeted finance personnel in small businesses, local government, churches and non-profit organisations.
Don Jackson, director of threat intelligence at SecureWorks, said although a connection between the arrests has not been confirmed, several of the money launderers arrested in the US are connected with some of the largest Zeus operations around the world.
Online banking fraud is not just an Eastern European problem, but a lot of these types of tools are developed in places like Russia and Eastern European countries, so it is not surprising the hackers are originally from these regions, he said.
Mickey Boodaei, chief executive at Trusteer, said the arrests in the UK and US indicate that financial fraud is not the business of individuals.
"Behind these operations you can find groups of people which in many cases operate for larger organised crime groups that have the money to run large scale criminal online operations," he said.
Other cybercrime gangs are almost certainly operating in other countries in continental Europe, Canada and across the Asia-Pacific region, running parallel criminal operations to the Zeus gangs in the UK and the US, said Boodaei.
But he said the arrests also show that law enforcement agencies, with the help of the banks, their customers and the industry, are capable of tracking these people down and putting them behind bars.
"More efforts are needed for this promising start to become truly successful. Financial fraud can be stopped from spreading if financial organisations and customers continue to improve security and work with law enforcement to go after cyber criminals," he said.