Which type of malware is often used to modify or exploit backdoor access in a system?

The correct answer is associated with a type of malware known for creating hidden channels of access that attackers can utilize to gain control over a system. This malware often disguises itself as legitimate software, luring users into executing it without realizing its malicious purpose.

When a Trojan is executed, it can modify or exploit existing vulnerabilities or backdoor access within a system. Once installed, it can provide attackers with remote control over the infected device, allowing them to execute commands, steal sensitive information, or facilitate further exploits. The insidious nature of Trojans lies in their ability to appear harmless while performing harmful activities in the background.

In contrast, other forms of malware have different primary functions. Ransomware is designed to encrypt files and demand payment for their release, while spyware primarily focuses on gathering personal information without the user's consent. A rootkit, although it can provide backdoor access, often aims to conceal its own presence and may not be directly responsible for creating the initial path of exploitation. Thus, the Trojan stands out as the most relevant choice for modifying or exploiting backdoor access.