Which type of malware accesses the victim's computer or network without the user's knowledge?

The type of malware that accesses the victim's computer or network without the user's knowledge is a backdoor. A backdoor is a method of bypassing normal authentication procedures, often created by an attacker to gain unauthorized access to a system while avoiding detection. This means that once installed, a backdoor can allow the attacker to exploit the system freely, adjusting settings, stealing data, or even deploying additional malware without alerting the user.

In contrast, a Trojan Horse is designed to mislead users into thinking it is a legitimate application, tricking them into installing it, but it does not inherently provide unauthorized access after its installation. Ransomware, on the other hand, typically encrypts files or systems and demands payment for their restoration, which is a more overt action than stealth access. A rootkit is a collection of tools that allows unauthorized users to access a computer while concealing its presence, but it is often used to maintain access rather than specifically gaining entry. Thus, backdoors are specifically created for stealthy access and are noteworthy for allowing attackers to manipulate systems without the user's awareness.