Security researchers have urged gaming companies to crack down on virtual currency auction and sales sites, reckoning criminals are cashing in to launder stolen money.

The research team at Trend Micro says most black hats steal the currency using online game exploits or by using malware and phishing to compromise players, selling the credit for cash on so-called real-money trading (RMT) platforms.

All major game titles are targeted, namely World of Warcraft - which has a huge number of players, most recently pegged at more than 5.5 million - and a large amount of in-game items and currency.

Trend Micro researchers say the currencies are sold on specialised auction sites, social media accounts, and on the dark web for real-world money which is then converted to anonymous cryptocurrency like Bitcoin.

"First, the cybercriminals acquire the game currency, usually by exploiting bugs and loopholes in the game or by stealing it from player accounts," the researchers say in the report [PDF].

"This laundered currency can therefore be used in multiple ways, from buying even more online game currency to sell, to cash out for real-world expenses, or funding cybercriminal operations.

"Companies that are also involved with the games abused in such a manner should also move to address these websites and contribute to the effort of taking them down, or if not, simply to monitor them further for cybercriminal activity."

The research team says RATs (remote access trojans) are the modern preferred method of compromising gamers to access their accounts and steal currency and items.

Information gathered by those trojans can include banking data, which gives criminals more avenues to earn money.

Phishing with fake game login pages to steal gaming credentials is also popular, along with the discovery and exploitation of vulnerabilities and glitches.

They say the auction sites such as playerauctions are slick polished exchanges indicative of the booming and lucrative gaming currency market.

Researchers point to the existence of sweat shop currency camps and the litany of defrauded players in urging gamers not to buy auction currency.

"Online gamers should realize the real-world consequences of what they do, and consider that their decision to take shortcuts (through gaming obstacles) may have a bigger impact," they say. ®