The three men, all in their twenties, are believed to be part of a criminal gang that e-mailed blackmail threats to online gambling sites. They allegedly use thousands of compromised "zombie" computers to launch distributed denial of service attacks if no money was given.
A Web site suffering from the attack would be flooded with unwanted network traffic, preventing it from being accessed by legitimate customers.
"Online betting Web sites suffering a denial of service attack would be literally blasted off the Internet and could cost them a fortune in lost revenue," said Graham Cluley, senior technology consultant for Sophos.
"An ever-growing criminal element, be they blackmailers or virus writers, are seeing the opportunity for launching significant attacks against Web sites via zombie computers. All PC users should ensure their computers are properly protected from being misused in this way," Cluley said.
The UK's National High Tech Crime Unit (NHTCU) is working with the Russian Ministry of Internal Affairs to investigate who might be behind the extortion attempts, after a gambling Web site complained it had had to pay protection money to keep its Web site open.
Law enforcement agencies in Australia, Canada, Estonia and the United States are also helping the British investigators in tracing the money transfers to Russia. The Russian police have seized a number of computers belonging to the men which may shed more information on activities of the gang.
Authorities do not know for certain how much money the group may have netted from betting companies, but the figure is believed to be in the hundreds of thousands of dollars, according to Felicity Bull, a spokeswoman for the NHTCU.
