Rootkit是指其主要功能为：隐藏其他程序行程的软件，可能是一个或一个以上的软件组合；广义而言，Rootkit也可视为一项技术。在今天，Rootkit一词更多地是指被作为驱动进程，加载到操作系统内核中的恶意软件。因为其代码运行在特权模式之下，从而能造成意料之外的危险。最早Rootkit用于善意用途，但后来Rootkit也被骇客用在入侵和攻击他人的电脑系统上，电脑病毒、间谍软件等也常使用Rootkit来隐藏踪迹，因此Rootkit已被大多数的杀毒软件归类为具危害性的恶意软件。Linux、Windows、Mac OS等操作系统都有机会成为Rootkit的受害目标。

A rootkit is a collection of computer software, typically malicious, designed to enable access to a computer or areas of its software that would not otherwise be allowed (for example, to an unauthorized user) while at the same time masking its existence or the existence of other software. The term rootkit is a concatenation of "root" (the traditional name of the privileged account on Unix-like operating systems) and the word "kit" (which refers to the software components that implement the tool). The term "rootkit" has negative connotations through its association with malware.