Final answer:
A rootkit is a type of malware that includes tools designed to hide malicious activity and other malware from detection. It gives attackers privileged access and can be difficult for antivirus programs to detect.
Step-by-step explanation:
The type of malware that consists of a set of software tools used by an attacker to hide the actions or presence of other types of malicious software, such as a virus, is known as a rootkit. Rootkits are designed to conceal malicious activities going on in an infected system, making it difficult for standard antivirus software to detect and remove the infection. They often give the attacker privileged access to the system and can be used to maintain a stealthy foothold on the system without the user's knowledge.