Which tool would primarily perform intrusion detection on a network?

The chosen answer is accurate because an Intrusion Detection System (IDS) is specifically designed to monitor network traffic for suspicious activities and potential threats. It analyzes incoming and outgoing network traffic, identifies patterns that may indicate a security breach, and alerts the network administrator if it detects any malicious activity.

An IDS can operate in two main modes: network-based, which monitors traffic on the network, and host-based, which focuses on the individual host's activities. This functionality is critical in maintaining the security posture of an organization, as it acts as a surveillance tool that helps detect unauthorized access attempts, unusual traffic patterns, and other anomalies indicative of intrusions.

In contrast, other tools mentioned in the options serve different primary functions. A Virtual Private Network (VPN) is used to create secure connections over the internet, ensuring privacy and data security for users. A firewall primarily serves to filter incoming and outgoing network traffic based on predefined security rules, but it does not actively monitor network behaviors for threats as an IDS does. Data Loss Prevention (DLP) focuses on preventing sensitive data from being accessed or transmitted outside of the organization's network, making it a different class of security tool altogether.