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An easier approach is to fool game DRM software into thinking its reading data for playing a game from its original CD rather than from an on-disk copy. DRM software uses a number of techniques to try to defeat that trick, but a straightforward one is simply to detect if CD emulation software is present on the system and if so, if the game is being run from an on-disk emulated copy. That’s where rootkits come in. Two of the most popular CD emulation utilities are Alcohol and Daemon Tools and they both use rootkits.