What is a key characteristic of an intrusion detection system?

A key characteristic of an intrusion detection system (IDS) is its ability to analyze both incoming and outgoing network traffic for potential threats. This function allows the system to monitor network activity in real time, identifying suspicious patterns or known attack signatures. By assessing traffic in both directions, an IDS can provide a comprehensive view of network security and detect a variety of threats ranging from external attacks to internal policy violations.

In contrast to the other options, the focus on analyzing both types of traffic is essential for the effectiveness of an IDS. This characteristic enables it to perform its primary role of threat detection and alerting administrators to potential security breaches. It's important to note that while some systems may block threats (as indicated in one of the options), an IDS typically focuses on monitoring and alerting rather than blocking; that is often the role of an Intrusion Prevention System (IPS). Additionally, while user intervention may sometimes be involved in managing an IDS, its primary purpose is to continuously monitor traffic without needing constant human oversight.