Which security solution is responsible for filtering unwanted email based on predetermined criteria?

The chosen answer refers to spam filtering, which is specifically designed to identify and manage unwanted or unsolicited email, commonly known as spam. This process utilizes various predetermined criteria such as keywords, sender reputation, and patterns of behavior to determine whether an incoming email should be classified as legitimate or spam. By actively filtering out unwanted messages before they reach a user's inbox, spam filtering not only enhances productivity but also protects users from potential phishing attacks and malicious content often found in spam emails.

In contrast, the other options serve different roles within cybersecurity. A web application firewall (WAF) is intended to protect web applications by filtering and monitoring HTTP traffic between a web application and the internet, focusing on threats like SQL injection and cross-site scripting. A proxy server acts as an intermediary for requests from clients seeking resources from other servers, providing anonymity and content filtering primarily for web traffic. An intrusion prevention system (IPS) is designed to detect and prevent identified threats by monitoring network traffic for suspicious activities and taking action to block them. Each of these solutions plays a critical role in the cybersecurity landscape but is not specifically tailored for managing email content as spam filtering is.