A rootkit is a program (or combination of several programs) designed to take fundamental control (in Unix terms "root" access, in Windows "Administrator" access) of a computer system, without authorization by the system's owners and legitimate managers. Access to the hardware (i.e., the reset switch) is rarely required as a rootkit is intended to seize control of the operating system running on the hardware. Typically, rootkits act to obscure their presence on the system through subversion or evasion of standard operating system security mechanisms. Often, they are Trojans as well, thus fooling users into believing they are safe to run on their systems. Techniques used to accomplish this can include concealing running processes from monitoring programs, or hiding files or system data from the operating system. Rootkits may have originated as regular applications, intended to take control of a failing or unresponsive system, but in recent years have been largely malware to help intruders gain access to systems while avoiding detection. Rootkits exist for a variety of operating systems, such as Microsoft Windows, Linux and Solaris. Rootkits often modify parts of the operating system or install themselves as drivers or kernel modules, depending on the internal details of an operating system's mechanisms.