A rootkit is a type of malware that enables cyber criminals to gain access to and infiltrate data from machines without being detected. It covers software toolboxes designed to infect computers, give the attacker remote control, and remain hidden for a long period of time1 One of the most prominent characteristics of a rootkit is that it cannot be detected by antivirus because of its masking techniques. A rootkit may be able to subvert the software that is intended to find it, such as by hooking system calls, modifying kernel objects, or tampering with the registry2 Another prominent characteristic of a rootkit is that it takes control of the operating system. A rootkit may install itself in the kernel or the firmware of the device, giving it the highest level of privilege and access. A rootkit may also replace the bootloader or the BIOS of the machine, making it difficult to remove. A rootkit can use its control over the operating system to launch other malware, such as ransomware, bots, keyloggers, or trojans34 References:

1: What Is a Rootkit? How to Defend and Stop Them? | Fortinet

2: Rootkit - Wikipedia

3: What Is a Rootkit? – Microsoft 365

4: What is Rootkit? Attack Definition & Examples - CrowdStrike