How does a Virus typically spread within a network?

A virus typically spreads within a network primarily by being loaded onto a user's computer without consent. This can occur through various means, such as sharing infected files, downloading software from untrustworthy sources, or through email attachments. Once the virus is executed on a computer, it can begin to replicate itself and spread to other systems on the same network, often exploiting vulnerabilities in software or network protocols.

This method of spreading relies on user interactions or system vulnerabilities rather than the more passive actions suggested in other choices. For example, while intercepting packet data may involve malicious activities, it is more characteristic of certain types of network attacks (like man-in-the-middle attacks) rather than how traditional viruses propagate. Observing individuals for sensitive data also entails a different operation, focusing on information theft rather than active infection. Creating virtual environments refers to the usage of sandboxing or virtualization technologies to safely execute potentially harmful applications, which is more aligned with testing programs than with how a virus spreads.