Valve Anti-Cheat

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Valve Anti-Cheat, abbreviated to VAC, is a proprietary anti-cheat solution developed and maintained by Valve Corporation as a component of the Steam platform. Although predating Steam, VAC has been fully adapted to its network and, since the release of VAC2, has seen considerable success in the constant battle against cheating in online games.

VAC was first released with Counter-Strike 1.4 in 2002,^[1] 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 20 June 2005 launch VAC2 has successfully overseen a decline in the number of cheating players across games "protected" by it.

VAC2 has been implemented in GoldSrc, Source, and Unreal Engine 2 titles. It is included in the Steam SDK for licencees.

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,^{[citation needed]} again denying cheat producers information.

Disadvantages

A 'content hack', which cannot be directly detected by VAC2.

• 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.^[2]

Successes

On June 20, 2006, a prominent cheat distributing source "informed the top cheat distributing sites to mark all cheats as [VAC] detected until further notice", citing VAC's hash matching as the reason why cheat users were routinely and frequently receiving bans, even though the VAC code on client computers had not been altered for some months.^{[citation needed]} There have been no publicly acknowledged breakthroughs in circumventing VAC's protection since, although private cheats may still exist for the few who have access to them.^{[citation needed]}

On November 17, 2006, Valve announced that "new [VAC] technology" had caught "over 10,000" cheating attempts in the preceding week alone,^[3] the first real indication of the scale of anti-cheat operations. It should be noted that not all of the accounts banned would have contained legitimate, purchased games, and also that there is no external audit on the figure.

Delayed bans, criticism & rationale

VAC2's motives are often called into question due to its 'delayed ban' system. 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"^[4] that the account is permanently banned from "VAC Secure" servers^[5] across a relevant set of games (e.g. Valve's Source games, GoldSrc games, Unreal engine games).

Valve's reasoning behind this delay system is that it makes it harder for cheaters to tell if the cheat is 'VAC-Proof' or not.^{[citation needed]} They claim that in the time it takes from the cheat being detected to the first banning, many more cheaters will have been caught than had it banned the first person on the spot and allowed the alarm to be raised immediately. Critics argue that this gives cheaters a counter-productive 'grace period' where they can freely cheat with no repercussions, however.^{[citation needed]}

Others charge the system (delayed bans or not) with existing to make Valve money,^{[citation needed]} on the basis that cheaters will buy another copy of the game in order to continue cheating rather than desist. While it is not unknown for cheaters to steal copies from shops in order to do this, the purchasing of new ones has only been reliably observed in those caught and reformed, mainly through their apologetic posts on the Steam User Forums.

Another criticism is that delayed bans increase the public's exposure to cheaters, and may drive otherwise innocent parties to install cheats of their own.

False-positive detections

Those that have been caught by VAC also criticise it, usually with the claim that it has made a false positive. Here a distinction must be made between false positives caused by incorrect detection, and grey-area false positives caused by correctly-identified code modifications which do not actually offer an unfair advantage.

• There are three recorded instances of incorrect detections, all under VAC1 and all quickly rescinded and reversed. These were:
  1. Physical RAM corruption.^{[citation needed]}
  2. The effect of running the VAC-protected game through the WineX software compatibility layer for Linux.^[6]
  3. An apparent server-side glitch on 2004-04-01.^[7]
• There are three recorded instances of the "benign cheats" described above triggering bans. These were:
  1. VAC1: HLamp, which allowed the user to control Winamp from the game's interface. Detection later reversed, and all bans caused by it rescinded.
  2. VAC2: The X-Spectate tool, which allowed server administrators to enable a wallhack effect while spectating to help decide if another player was doing the same. Later downgraded to a kick from the server, but bans not rescinded.
  3. VAC2: The single-player Half-Life modification Paranoia, which made changes to the engine's renderer that propagated to multi-player games.^[8]

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.

See also

• Cheating in online games
• PunkBuster
• Warden (software)
• Steam (content delivery)

References