Thanks to its explosive success, the online gambling industry is now ripe for extortion and distributed denial of service (DDOS) attacks.

Last April, UK-listed Betfair fell victim to a DDOS attack that took down its betting exchange and fixed-odds sportsbook. Malta-licensed Betat Casino also reported a DDOS attack from assailants who asked for 10 Bitcoin, or about $2,200, in order to stop the harassment.

New Jersey sites were also not immune to DDOS attacks. Last July, four of the state’s licensed online gambling operators experienced an initial wave of data flooding their sites for half an hour. According to the Division of Gaming Enforcement, the hacker warned of more sustained and powerful attacks unless the sites pay an unspecified amount of Bitcoin currency.

DDOS can be harmful for online gambling sites, where 60 percent of the transactions are carried out in real time. IT security specialist Gold Security said an hour of unmitigated DDOS means $40,000 lost for a business.