IDS (Intrusion Detection Systems) and IPS (Intrusion Prevention Systems) are fundamental network security mechanisms responsible for monitoring infrastructure traffic and events, helping protect the network against threats. The main difference between them is that an IDS is a passive tool, whereas an IPS operates actively.

This means an IDS monitors network or host traffic without directly intervening. It looks for unwanted system manipulations—such as unauthorized logins, incorrect privileges, suspicious activities, unusual access times, atypical requests for restricted data, and massive access attempts originating from a single source. Based on these analyses, the IDS generates alerts that administrators can use to investigate potential security incidents.

IDS can be classified by the methods they use to identify intrusions, such as signature-based (or misuse), anomaly-based, and specification-based detection.

• Popular tools: Snort, Suricata, Zeek, and OSSEC.

• Main advantages: A very low impact on network traffic and the ability to conduct in-depth analyses of logged events.

On the other hand, because an IPS operates actively, it goes beyond simply monitoring traffic and detecting threats. It actually triggers security countermeasures, allowing it to block or interrupt attacks in real time. By operating inline within the network flow, it enables an automated response to identified events, significantly reducing the need for immediate human intervention.

Like an IDS, an IPS can also be classified by its detection method (signature or anomaly).

• Popular tools: Suricata (which can operate as both an IDS and an IPS), Snort IPS, Cisco Firepower IPS, and Palo Alto Threat Prevention.

Although some consider the IPS to be an evolution of the IDS, it does have a few distinct drawbacks in comparison. These include:

• The risk of critical false positives, which can end up blocking legitimate access.

• A heavier impact on network performance, due to the need to analyze and make direct decisions on live traffic.

• The potential to become a single point of failure in the network.

• Higher costs and increased complexity in both configuration and maintenance.