What type of malware completely replaces an existing application?

A virus is a type of malware that can attach itself to an existing application or file and replicate itself. When a virus infects a program, it can replace the original code, effectively modifying the application and potentially causing harm or unwanted behavior. This ability to replace an existing application, including its core functionality, distinguishes it from other types of malware.

Worms are self-replicating malware that spread across networks, often without needing to attach to a host application. Trojan horses disguise themselves as legitimate software but do not typically replace existing applications; they might install additional malicious software. Spyware focuses on gathering information from the user, without altering the functionality of existing applications. These characteristics reinforce the unique qualities that identify a virus as the type of malware that can completely replace an existing application.