What is the primary purpose of spyware?

The primary purpose of spyware is to capture user account data and passwords, which is why option C is the correct choice. Spyware is a type of malicious software that is designed to infiltrate a user's system without their consent. Once installed, it can monitor and track activities, gather sensitive information such as login credentials, personal details, and other private data, and then send that information back to the attacker or a remote server. This makes it a significant threat to individual privacy and security as it compromises sensitive information without the user's knowledge.

In contrast, improving network efficiency is not within the scope of spyware's functions; rather, that could be the goal of legitimate network management tools. Enhancing user experience could imply legitimate software designed for usability, which is again not applicable to spyware, as it typically degrades it instead of enhancing it. Lastly, while data backups are crucial for security, spyware does not serve the purpose of backing up data, as it instead focuses on data theft and user surveillance.