Final answer:
Privacy filters on computer screens are designed to protect against 'shoulder surfing' by restricting the visibility of a screen's content to the front-on viewer. They prevent others from gaining sensitive information by looking at the display and are not a defense against software threats or cyberattack methods.
Step-by-step explanation:
Privacy filters are physical layers applied over a computer screen to limit the viewing angle, so that the screen's content can only be seen clearly from a direct, front-on perspective. This is used to mitigate the risk of shoulder surfing, which is a type of security risk where an unauthorized person may gain sensitive information by directly looking at another user's display. The application of a privacy filter does not directly protect against software-based threats such as rootkits, cyberattacks like spear phishing, or broader strategies like social engineering; rather, it provides a safeguard against visual breaches of privacy and data security in physical environments.