There are now an estimated 15,000 such sites on the World Wide Web, including some 13,000 illegal ones, shuffling around 15 billion euros (23.6 billion dollars) a year, according to the authorities.
These dizzying figures have finally stung sports authorities into action.
Late last year, International Olympic Committee (IOC) president Jacques Rogge compared the gambling issue to the gangrene caused by doping in sports.
He proposed the creation of a world surveillance agency based on the model of the World Anti-Doping Agency (WADA), which leads the fight against drugs in sport.
The explosion of Internet sports betting, which has flowed across national borders that previously confined gamblers, has created a virtual market that is controlled mostly from Asia.
On these sites, gamblers have been known to lose large sums of money, either fairly or increasingly as victims of fraud, a trend that is threatening the credibility of sport.
Declan Hill, a journalist and British expert on the problem, says the amount of corruption in global sports has increased almost 100-fold in the past five years thanks to Internet-based gambling.
"Ten years ago, national lotteries controlled 100 percent of the sports (betting) market," Hill said.
"Today, the French National Lottery, for example, controls only 25 percent of the French market, but their number of clients has multiplied by four times," he said.
The problem has continued almost unabated since 2006, when a study conducted by the independent Information Systems Security Consulting firm warned of the criminalisation of Internet sports betting.
"The sector of online gaming is today mostly controlled by criminal groups," the security firm said in the study commissioned by a group of European state lotteries.
Players had been approached and threatened, referees influenced, and matches bought, it found.
This is the form of corruption that threatens the credibility of sport the most but more common is money laundering, which seems to have become almost routine, based on the amounts of money paid through certain less profitable websites, even for sporting events of little significance.
Alarmingly, the amount of money traded on a single website can surpass 100,000 euros for a match in the third division football in Romania, or even the first division of the Czech women's league.
Experts estimate that 85 percent of these websites have been created for the sole purpose of "washing away" dirty money.
Sports federations -- notably for tennis, football and cricket, the pioneers in the fight against harmful effects of illegal gambling -- have become increasingly worried about the issue.
But, apart from fears about the tarnished image of their sport, at the same time they are trying to secure a financial stake for themselves from the booming phenomenon.
Each year, French gamblers place sports bets worth more than 510 million euros on the Internet.
Of this, only around 12 million euros is believed to be legal, by means of the French National Lottery, the only authorised online sports betting operator in the country.
Following the example of the French Tennis Federation, a number of sports bodies are trying to claim part of the lucrative Internet betting industry on the model of television broadcasting agreements.
The federation has accused various sites of offering illegal betting in violation of the exclusive rights it has to commercially exploit its events.
A court judgement is expected to set a legal precedent in the coming days, in the glare of the world media as Paris hosts the French Open.