According to internet security researchers, criminals use VPNs and online currency such as Bitcoins to fund their accounts at online gambling sites. Due to the high volume, lack of regulations, and using Tor, criminals are able to wash their money and cash out the proceeds from cyber crime.
Back in 2003, online gambling sites paid out $9.1 Billion in winnings. By 2013, the amount of cash paid out by online sites increased to $32.7 Billion.
Although the number of online gambling sites fluctuate due to closures, there are at least over 25,000 online gambling sites in operation around the world, according to McAfee.
Source: Teri Robinson, “Online gambling provides cover for money laundering, study says,” SC Magazine, April 25, 2014.