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The Valve Anti-Boost System (VAB)
Because nobody likes playing with Silver.
Playing games should be fun. In order to ensure the best possible online multiplayer experience, Valve developed a state-of-the-art anti-Boost system that automatically detects and permanently rank any player using boost on a VAB secured server. What this means to you as a player is that you don't have to worry about annoying booster getting an unfair advantage and disrupting your game.
The Valve Anti-Boost system is only enabled on servers with the secured shield logo and only Valve has the ability to VAB boost a user. While server admins may choose to rank up players from playing on their specific servers, they do not have the ability to VAB boost players. The VAB system is automated and contacting Steam Support to join booster isn't necessary. Valve has a zero-tolerance policy for silver and will not lift VAB rank under any circumstances.