Game maker Valve is threatening to shut down sites dedicated to gambling with add-ons to its popular Counter Strike game.
On Thursday the company sent cease and desist letters to 23 sites, demanding that gambling operations be stopped, and that the sites had 10 days to comply. The row revolves around the software overlays that change the appearance of the characters people play in Counter Strike: Global Offensive (CSGO) and the weapons and other virtual items
"We are aware that you are operating one of the gambling sites listed below," wrote Karl Quackenbash, general counsel to Valve Corporation, in the letter sent out to various sites. "You are using Steam accounts to conduct this business. Your use of Steam is subject to the terms of the Steam Subscriber Agreement ('SSA')."
Last week the company reiterated that its user agreements ban external sites from asking users to connect their Steam accounts in order to trade items for real money. The company added that it would use "all available remedies" against sites that did not stop players using virtual goods to gamble.
Among those listed are CSGO Lotto, CSGO Wild and CSGO Diamonds, each among the most popular gambling sites.
Notoriety of the practice rose following news that two prominent gamers, Trevor Martin and Tom Cassell, were promoting the CSGO Lotto website to their viewers, without properly disclosing that they owned and ran it.
Subsequently complaints also arose that Valve had not done enough to police the marketplace on the Steam service to stop the gambling, leading to a lawsuit filed by a player.
Research from Eilers & Krejcik Gaming in April estimates that $2.3 billion in skins were wagered on esports in 2015. A new report suggests the industry could have seen the total value of wagers rise to $7.4 billion this year.
