Playtesters had to rigorously test the mechanics of a game and introduced cheat codes to make this process easier.
[2] 1983 advertisements for "The Great Escape Utility" for Castle Wolfenstein (1981) promised that the $15 product "remodels every feature of the game.
The Commodore 64, Amstrad CPC range and ZX Spectrum also allowed players with the proper cartridges or Multiface add-on to freeze the running program, enter POKEs, and resume.
In order to find them a hacker had to interpret the machine code and locate the critical point where the number of lives is decreased, impacts detected, etc.
Generally, the majority of cheat codes on modern day systems are implemented not by gamers, but by game developers.
[6] In many cases, developers created cheats to facilitate testing, then left them in the game as they expanded the number of ways people could play it.
Yet other games, such as those using the Source engine, allow developer consoles to be used to activate a wide variety of cheats in single-player or by server administrators.
However, cheating in such games is nonetheless a legal grey area because there are no laws against modifying software which is already owned, as detailed in the Digital Millennium Copyright Act.
[9] Cheat codes are usually activated by typing secret passwords or pressing controller buttons in a certain sequence.
[10] Less common activation methods include entering certain high score names, holding keys or buttons while dying, picking up items in a particular order and otherwise performing unintuitive actions.
For example, using cheat codes from Doom in Heretic gives the opposite of the desired effect, such as instant death instead of invulnerability or stripping weapons instead of providing them.
"[13] A bot is a type of artificial intelligence (AI)–based expert system software that plays a video game in the place of a human, to perform actions (repetitive or not) that enable advantages to be achieved.
An early example is the Multiface for the ZX Spectrum, and almost every format since has had a cheat cartridge created for it; such as Datel's range of Action Replay devices.
The legality of this type of devices has been questioned, such as in the case of Lewis Galoob Toys, Inc. v. Nintendo of America, Inc., in which Nintendo unsuccessfully sued Lewis Galoob Toys stating that its cheating device, the Game Genie, created derivative works of games and thus violated copyright law.
In the cracker group release lists and intros, trained games were marked with one or more plus signs after them, one for each option in the trainer, for example: "the Mega Krew presents: Ms. Astro Chicken++".
In the case of Jet Set Willy on the ZX Spectrum computer, a popular cheat involved replacing a Z80 instruction DEC (HL) in the program (which was responsible for decrementing the number of lives by one) with a NOP, effectively granting the player infinite lives.
An alternative method for cheating in online games involves modification of inbound or outbound network traffic between the client and server.
[18] For example, if a player was unsure whether an enemy was present in a room, they could activate the lag switch to block network traffic momentarily.
Once the player had gathered the necessary information about enemy locations, they could deactivate the lag switch and resume normal play.
More modern methods typically involve lower level packet editing or forgery in a "Man-in-the-middle attack" style.
For example, symmetric encryption keys could be read from the game's memory, granting access to inbound packets.
In online multiplayer games, a player may use macro scripts, which automatically find items or defeat enemies.
The rise of virtual economies has led to cheating where a gamer uses macros to gain large amounts of in-game money which the player will then trade for real cash.
[25] The Terms of Service of most modern online games now specifically prohibit the transfer of accounts or the sale of in-game items for 'real-world' money.
The enforcement of these terms varies however from one company to another, many turning a blind-eye to such trading as detection and prevention requires resources and banning players also results in losses of revenue.
Some online games, such as Battlefield 1942, include specific features to counter cheating exploits, by incorporating tools such as PunkBuster, nProtect GameGuard, or Valve Anti-Cheat.