The iTunes Store uses Apple's FairPlay digital rights management (DRM) technology. FairPlay is built into the MP4 multimedia file format as an encrypted AAC audio layer, and is used by the company to protect copyrighted works sold through the store, allowing only authorized devices to play the content.[95][96] The restrictions imposed by FairPlay, mainly limited device compatibility, have sparked criticism, with a lawsuit alleging antitrust violation[97] that was eventually closed in Apple's favor,[98] and various successful efforts to remove the DRM protection from files,[99][100] with Apple continually updating its software to counteract such projects.[101]