A gang of alleged cyber-extortionists arrested in Russia last week are accused of costing UK online bookmakers massive amounts of money through lost business.
Russian police said on Wednesday that the ring of hackers caused about £40m in damage, according to the Associated Press.
Yevgeny Yakimovich, the chief of the Russian Interior Ministry's Department K, which tackles cybercrime, told journalists in Moscow that the gang launched distributed denial-of-service attacks at nine UK bookmakers. They then demanded up to $50,000 (£28,000) before they'd stop the attacks.
Two unnamed companies paid up, Yakimovich said.
As reported last week, the UK's National Hi-Tech Crime Unit (NHTCU) played a major role in breaking up the gang.
Earlier this year one UK bookmaker, who wished to remain anonymous, said his firm had been attacked several times. The gangs would typically contact the online firms through a customer-service email address on the Web site with a demand for between £10,000 and £30,000 as well as a warning that if it wasn't paid then a distributed denial of service (DDoS) attack would be launched against the site during peak traffic hours.
The bookie said all the UK firms had refused to pay the ransom and had been working with the NHTCU to combat the attacks, but admitted the cost of putting extra IT security measures in place was as much as £100,000 for some firms.
Blue Square was one of the firms that publicly admitted to being targeted after its site was taken down by blackmailers flooding it with a DDoS attack.
Betfair also revealed last month that during Euro 2004 it was hit by a DDoS attack that caused disruption to its service.
Silicon.com's Andy McCue contributed to this report