Organised crime gangs are trying to blackmail Internet betting sites on the eve of American football's Super Bowl by threatening a crippling data attack unless they pay a "protection" fee.
The National Hi-Tech Crime Unit (NHTCU) said it is investigating a series of attacks and threats of attacks on companies in the United Kingdom. Security experts say sites based in the Caribbean and continental Europe have also been targeted.
"These are not groups of amateur hackers - great deals of money are changing hands," said an NHCTU spokesman. "These are for-profit crimes and all intelligence suggests that organised crime is involved."
One such target is Curacao-based VIP Management Services, which runs seven gambling sites. "We were first targeted in September and have been under intermittent attack ever since," said Mr Alistair Assheton, managing director of the privately held six-year-old firm.
The so-called denial-of-service attacks, which can disable a corporate data network with a barrage of bogus data requests, are a standard tool for hackers aiming to knock out a site.
Security experts and police said they believe the gangs are based in Eastern Europe and Russia, taking advantage of the region's weak cyber-crime laws and its legions of savvy programmers.
Reuters obtained a copy of an e-mail extortion threat distributed earlier this month that demanded sites pay $15,000 for six months' worth of protection.
"If you wait to make a deal with us when the attacks start, it will cost you $25,000 for six months protection and the lost revenues as your site will stay down until the $25,000 is received," the e-mail said.