Two British and one Finnish men have been arrested on suspicion of wreaking havoc with computer viruses.
The three computer programmers have targeted UK businesses since 2005, infecting thousands of computer worldwide via spam emails carrying virus attachment.
The group, who are suspected to be members of an online community known as M00P, kept one step ahead of security software by constantly writing new viruses.
Detective Constable Bob Burls of the Computer Crime Unit at London's Metropolitan Police said to Reuters that the men may be connected by an online company.
"We believe the suspects created and adapted viruses with the aim of causing massive infection by spamming", said the detective.
The viruses that are believed to have been spread by the group infect computers and allow the hackers access to personal and commercial data.
Finnish and British police worked together to coordinate the investigation and arrests.