Which type of malware can self-replicate and spread across networks?

The correct answer is the type of malware known as a worm. Worms are specifically designed to self-replicate and are capable of spreading independently across networks without needing any user intervention or attachment to other files or programs. They exploit vulnerabilities in network systems to propagate themselves, which allows them to infect multiple devices rapidly.

In contrast, a Trojan masquerades as a legitimate program to trick users into running it, but it does not replicate itself or spread; instead, it relies on social engineering tactics to gain access. A virus also requires a host program to attach itself to and spreads when that program is executed, often traveling with files or software rather than independently. Ransomware, while malicious and threatening the integrity of data, primarily functions by encrypting data and demanding payment, and it does not inherently have the capability to replicate and spread across systems like a worm does.

Understanding the distinct characteristics of different types of malware helps in devising effective security measures and mitigation strategies against them.