Valve Anti-Cheat, abbreviated to VAC, is an anti-cheat solution developed by Valve Corporation as a component of the Steam platform.
History
VAC was first released with Counter-Strike 1.4 in 2002, following Valve's decision to forego PunkBuster in preference of a proprietary system. The initial version, VAC1, saw success for a period, but in March or April 2004 updates ran dry as the Valve engineers maintaining it moved on to the production of its successor, VAC2. VAC1 swiftly became virtually useless during this period of development, but since its June 20, 2005, launch VAC2 has successfully overseen a decline in the number of cheating players across games protected by it.[citation needed]
On November 17, 2006, Valve announced that "new [VAC] technology" had caught "over 10,000" cheating attempts in the preceding week alone, the first real indication of the scale of anti-cheat operations. Not all of the accounts banned would have contained legitimate, purchased games, and also that there is no external audit on the figure.
As of 2010, unofficial sources estimate that over a million Steam accounts have been banned by the VAC system.
VAC is also part of Steamworks.
Advantages
- Total integration through Steam, including using the Steam framework for any update tasks
- Delayed bans deny cheat producers accurate and timely information
- As of VAC2, client-side updates are not always required to detect new cheats, again denying cheat producers infotmstion.
Disadvantages
- Delayed bans (see below) means that cheaters are free to disrupt other players until their ban takes effect.
- This may entice others to cheat, taking an "if they can do it so can I" attitude.
- The burden of banning individual cheaters who have been detected by VAC but not yet banned remains on server administrators.
- This also leads to the skewing of statistics and ranking systems, even if the cheaters' data is removed when they are banned.
- VAC cannot detect 'content hacks', where, for example, texture transparency and color are manipulated, since they do not involve modification of any program code. In the Source engine the option to create "pure" servers (
sv_pure) that prevent custom content from overwriting the game's defaults was created to alleviate this.
[Delayed bans, criticism & rationale
If a cheat is found the player's Steam account will be flagged as cheating immediately, but the player will not receive any indication of the detection. It is only after a delay of "days or even weeks"[6] that the account is permanently banned from "VAC Secure" servers[7] for that game, along with other games that use the same engine. (e.g. Valve's Source games, GoldSrc games, Unreal engine games). Valve never discloses which cheat was detected.
False-positive detections
Some who are banned by VAC claim that it has made a false positive.
- There are four recorded instances of incorrect detections, all quickly rescinded:
- VAC1: On its initial release, VAC would issue bans for faulty memory. Valve quickly updated VAC to only kick for faulty memory[8] and reversed all bans for faulty memory.
- VAC1: The effect of running the VAC-protected game through the Cedega software compatibility layer for Linux.
- VAC1: An apparent server-side glitch on April 1, 2004
- VAC2: Over two weeks in July 2010, approximately 12,000 owners of Call of Duty: Modern Warfare 2 were banned when Steam updated a DLL file on-disk after it had been loaded into memory by the game. Those affected received a free copy of Left 4 Dead 2 and/or a gift copy to send to a friend.
Cheats may be hidden inside otherwise legitimate mod or skin downloads that are created to maliciously get innocent people banned. Since the source of a cheat installed on a computer cannot be proven, bans due to this are never rescinded.
According to Valve: "Valve has a zero-tolerance policy for cheating and will not lift VAC bans under any circumstances." This includes account hijacking and other circumstances beyond the control of the account's owner.
Manually-applied bans
In July 2010, several players who successfully used information leaked from Valve to increase their chances of crafting a special Team Fortress 2 item found themselves banned by VAC.
