Valve Anti-Cheat

Valve Anti-Cheat (VAC) is an automated anti-cheat system developed by Valve and first released with Counter-Strike in 2002 to enforce rules in online multiplayer games distributed through the Steam platform. The system detects unauthorized modifications to a game, including third-party software designed to manipulate gameplay, as well as alterations to core game files such as executable programs and dynamic-link libraries. Modifications that provide an unfair advantage are classified as cheats and are subject to detection by VAC.

When cheat software is detected on a user's system, VAC issues a permanent ban preventing access to VAC-secured servers for the specific game involved. Bans are applied automatically and may result from various factors, most commonly the detection of known cheat signatures. Enforcement may occur days or even weeks after the initial detection, depending on the game and circumstances.

Valve does not disclose to the player the date of detection, the type of cheat identified, or the specific method by which the cheat was detected. VAC bans are typically permanent and non-negotiable, although Valve retains the ability to remove them in certain cases, such as confirmed false positives, through internal review.

During one week of November 2006, the system detected over 10,000 cheating attempts, and during the month of December 2018 over 600,000 accounts were banned.