A type of Trojan that keeps itself, other files, registry keys and network connections hidden from detection. It enables an attacker to have "root" access to the computer, which means it runs at the lowest level of the machine. A rootkit typically intercepts common API calls. For example, it can intercept requests to a file manager such as Explorer and cause it to keep certain files hidden from display, even reporting false file counts and sizes to the user. Rootkits came from the Unix world and started out as a set of altered utilities such as the ls command, which is used to list file names in the directory (folder).|
Rootkits can also be used for what some vendors consider valid purposes. For example, if digital rights management (DRM) software is installed and kept hidden, it can control the use of licensed, copyrighted material and also prevent the user from removing the hidden enforcement program. However, such usage is no more welcomed than a rootkit that does damage or allows spyware to thrive without detection. See Trojan.