Which of the following statements best describes a companion virus?

A companion virus is a type of malware that creates an executable file that has the same name as a legitimate program but with a different file extension. By doing this, it tricks users into running the malicious file instead of the legitimate one, as the user may not realize that the file they are executing is a virus and not the intended program. This ability to mimic legitimate software is what makes companion viruses particularly deceptive and dangerous.

In contrast, the other choices describe different characteristics of malware types that are not specific to companion viruses. For example, ransomware generally encrypts files for ransom, but that doesn't apply to all viruses. Similarly, viruses that replicate without user intervention typically refer to viruses in general, whereas companion viruses specifically rely on the user executing the misleading program. Lastly, while some viruses can spread through networks, companion viruses do not typically propagate that way; they rely on user interactions to become activated.