IDS vs IPS vs Firewall

A very common query asked by network and security administrators is the difference between Firewall, IPS and IDS.

All the 3 terms related to providing security to network and are considered essential components of a Network especially Data Center Network.

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The main difference being that firewall performs actions such as blocking and filtering of traffic while an IPS/IDS detects and alert a system administrator or prevent the attack as per configuration.

A firewall allows traffic based on a set of rules configured. It relies on the source, the destination addresses, and the ports. A firewall can deny any traffic that does not meet the specific criteria.

IDS is a passive device which watches packets of data traversing the network, comparing with signature patterns and setting off an alarm on detection on suspicious activity. On the contrary, IPS is an active device working in inline mode and prevent the attacks by blocking it.

Furthermore, below table enumerates the difference between Firewall vs IDS vs IPS in detail –

PARAMETER	FIREWALL	IPS	IDS
Abbreviation for	-	Intrusion Prevention System	Intrusion Detection System
Philosophy	Firewall is a network security device that filters incoming and outgoing network traffic based on predetermined rules	IPS is a device that inspects traffic, detects it, classifies and then proactively stops malicious traffic from attack.	An intrusion detection system (IDS) is a device or software application that monitors a traffic for malicious activity or policy violations and sends alert on detection.
Principle of working	Filters traffic based on IP address and port numbers	inspects real time traffic and looks for traffic patterns or signatures of attack and then prevents the attacks on detection	Detects real time traffic and looks for traffic patterns or signatures of attack and them generates alerts
Configuration mode	Layer 3 mode or transparent mode	Inline mode , generally being in layer 2	Inline or as end host (via span) for monitoring and detection
Placement	Inline at the Perimeter of Network	Inline generally after Firewall	Non-Inline through port span (or via tap)
Traffic patterns	Not analyzed	Analyzed	Analyzed
Placement wrt each other	Should be 1st Line of defense	Should be placed after the Firewall device in network	Should be placed after firewall
Action on unauthorized traffic detection	Block the traffic	Preventing the traffic on Detection of anomaly	Alerts/alarms on detection of anomaly
Related terminologies	> Stateful packet filtering > permits and blocks traffic by port/protocol rules	> Anomaly based detection > Signature detection > Zero day attacks > Blocking the attack	> Anomaly based detection > Signature detection > Zero day attacks > Monitoring > Alarm