This is a malicious piece of software installed on a computer system to give privileged access levels to unauthorised individuals. The name is a combination of ‘root’, the name given to the administrative user on most Unix-like operating systems, and ‘kit’ as it usually comprises a selection of ready-made tools to make the software easy to deploy. Rootkits typically employ stealth techniques to avoid detection by their victims, but can be picked up and eliminated by effective antivirus software.