IDS vs IPS vs Firewall – Know the Difference


IDS vs IPS vs Firewall

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.


You can watch this video for better understanding:

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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 –

Abbreviation for
-Intrusion Prevention System
Intrusion Detection System
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
Inline at the Perimeter of Network
Inline generally after Firewall
Non-Inline through port span (or via tap)
Traffic patterns
Not 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


Download the IDS vs IPS vs Firewall difference table







Continue Reading:

Cisco IPS/IDS Interview Questions



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