What type of malicious software spreads by inserting itself into programs?

The correct answer is a virus, which is a type of malicious software that specifically spreads by attaching itself to programs. When a user executes an infected program, the virus activates and can replicate itself, spreading to other programs and files on the system, often without the user's knowledge. This self-replicating behavior is what distinguishes viruses from other types of malware.

Ransomware, while also malicious, primarily focuses on encrypting a user's files and demanding payment for their release, rather than embedding itself into other programs. Adware is designed to display unwanted advertisements on a user's device; it does not typically reproduce within other software like a virus does. Spyware collects information from a user's computer, often without their consent, but it does not replicate itself or spread by inserting into programs. Understanding these distinctions is crucial for recognizing various threats in cybersecurity.