Autorun.inf

An autorun.inf file is a text file that can be used by the AutoRun and AutoPlay components of Microsoft Windows operating systems. For the file to be discovered and used by these component, it must be located in the root directory of a volume. As Windows has a case-insensitive view of filenames, the autorun.inf file can be stored as AutoRun.inf or Autorun.INF or any other case combination.

The AutoRun component was introduced in Windows 95 as a way of reducing support costs. AutoRun enabled application CD-ROMs to automatically launch a program which could then guide the user through the installation process. By placing settings in an autorun.inf file, manufacturers could decide what actions were taken when their CD-ROM was inserted. The simplest autorun.inf files have just two settings: one specifying an icon to represent the CD in Windows Explorer (or "My Computer") and one specifying which application to run.

Extra settings have been added in successive versions of Windows to support AutoPlay and other new features.

autorun.inf is an ASCII text file located in the root folder of a CD-ROM or other volume device medium (See AutoPlay device types). The structure is that of a classic Windows .ini file, containing information and commands as "key=value" pairs, grouped into sections. These keys specify:

Autorun.inf has been used to execute a malicious program automatically, without the user knowing. This functionality was removed in Windows 7 and a patch for Windows XP and Vista was released on August 25, 2009 and included in Microsoft Automatic Updates on February 8, 2011.

The mere existence of an autorun.inf file on a medium does not mean that Windows will automatically read it or use its settings. How an inf file is handled depends on the version of Windows in use, the volume drive type and certain Registry settings.

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