Last week, Valve banned 90,000 Steam accounts, in an anti-cheating purge.
As this SteamDB graph shows, over 28,000 Steam accounts were banned on Wednesday 18 July, followed by over 60,000 on Thursday 19 July. The bulk of the bans were triggered by Valve Anti Cheat (VAC) measures, which suggests that VAC has identified a new exploit or form of cheating.
Valve has not commented on the spike in VAC bans, but the SteamDB graph shows that, in July 2018 alone, over 120,000 VAC bans have been applied to Steam accounts. Which is more or less par for the course – so far, the only month in 2018 which saw fewer than 100,000 VAC bans was June, with over 56,000 bans.
Valve’s attempts to tackle the perennial issue of cheating in multiplayer games, seen in that light, appear to be paying dividends in 2018, thanks to VAC. If you seek further information about VAC, have a look at this Steam forum.