What are rootkits and botnets?

A rootkit is a piece of software that can be installed and hidden on your computer without your knowledge. It may be included in a larger software package or installed by an attacker who has been able to take advantage of a vulnerability on your computer or has convinced you to download it (see Avoiding Social Engineering and Phishing Attacks for more information).

Rootkits are not necessarily malicious, but they may hide malicious activities. Attackers may be able to access information, monitor your actions, modify programs, or perform other functions on your computer without being detected.

Botnet is a term derived from the idea of bot networks. In its most basic form, a bot is simply an automated computer program, or robot. In the context of botnets, bots refer to computers that are able to be controlled by one, or many, outside sources. 

An attacker usually gains control by infecting the computers with a virus or other malicious code that gives the attacker access. Your computer may be part of a botnet even though it appears to be operating normally. Botnets are often used to conduct a range of activities, from distributing spam and viruses to conducting denial-of-service attacks (see Understanding Denial-of-Service Attacks for more information).

Why are they considered threats?

The main problem with both rootkits and botnets is that they are hidden. Although botnets are not hidden the same way rootkits are, they may be undetected unless you are specifically looking for certain activity. If a rootkit has been installed, you may not be aware that your computer has been compromised, and traditional anti-virus software may not be able to detect the malicious programs. Attackers are also creating more sophisticated programs that update themselves so that they are even harder to detect.

Attackers can use rootkits and botnets to access and modify personal information, attack other computers, and commit other crimes, all while remaining undetected. By using multiple computers, attackers increase the range and impact of their crimes. Because each computer in a botnet can be programmed to execute the same command, an attacker can have each of them scanning multiple computers for vulnerabilities, monitoring online activity, or collecting the information entered in online forms.