Intrusion Detection System (IDS)
A network security tool that monitors traffic for signs of malicious activity and alerts administrators without blocking it directly.
An intrusion detection system (IDS) is a network security tool that monitors traffic for known attack signatures or unusual behavior and alerts security staff when it spots something suspicious. Unlike an intrusion prevention system, an IDS observes and reports rather than automatically blocking traffic itself.
Because an IDS doesn't sit directly in the traffic path, it can analyze a copy of network traffic without risking any impact on network performance or accidentally blocking legitimate activity. Many organizations run an IDS and IPS together, using the IDS for broader visibility and the IPS for automated blocking of well-confirmed threats.