Which type of malware is specifically designed to remain undetected on a system?

The type of malware that is specifically designed to remain undetected on a system is a rootkit. Rootkits are particularly insidious because they operate at a low level within the operating system, allowing them to hide their presence from security tools and users. They can modify system components and processes so that the malware can run without drawing attention, often granting attackers persistent access to the compromised system.

In contrast, while spyware does indeed operate stealthily by collecting information about users, its primary goal is to gather data rather than maintain its presence undetected. A virus typically seeks to replicate and spread to other systems, which may not require it to remain hidden, whereas a Trojan disguises itself as legitimate software but does not inherently possess the same capabilities as a rootkit to hide deeply within the system. Thus, rootkits are specifically engineered for stealth and evasion, making them distinguishable in this context.