Valve's automatic anti-cheat detection system has gone on a banning spree following the company's most recent Summer Sale. Easily topping the previous record of 15,227 (according to Steam Database) from October 2016. The reason for it seems to be that cheaters had been buying games on the cheap on new accounts, with Valve cannily waiting until the end of the sale to ensure that they couldn't repeat the cycle. This is the largest amount of single-day bans from the auto-detection system. "VAC" stands for "Valve Anti-Cheat" - essentially, VAC is Valve's in-house method of detecting cheats installed on machines that are accessing its servers.
Users cheating isn't the only worry that the staff at Valve have on their minds as earlier this year the CS gaming community on Steam was plagued by a chat bot invasion in Counter-Strike: Global Offensive. Additionally, 4,972 accounts got banned due to in-game reports and this brought the total value of lost skins and other digital items to a $9,580, as pointed out in a report by Kotaku. This information comes from Steamdb, where you can see a steady graph of bans each day - and the graph for July 6 shows a massive spike. "If a VAC ban is determined to have been issued incorrectly, it will automatically be removed". There are illegal gambling types of operations that happen with some games, while other games just end up picking up players who try to cheat the system in other ways.