This has been an ongoing issue, essentially people unusually dedicated to ruining the game run multiple Linux VMs with bots. Valve has recently done a bit to im

This has been an ongoing issue, essentially people unusually dedicated to ruining the game run multiple Linux VMs with bots. Valve has recently done a bit to improve things after a community "save tf2" campaign, but it's a bit of a whack a mole situation. Practically joining a custom server with a moderator of some kind is the most effective option.