Difference between IDS and IPS

IDS VS IPS

Intrusion Detection Systems (IDS) and Intrusion Prevention Systems (IPS) are security technologies designed to identify and mitigate malicious activities in a network. While they share similarities, the key difference lies in their functionality and action. 

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1. Intrusion Detection System (IDS)

An IDS is a monitoring system that identifies suspicious or malicious activities in a network or system and generates alerts for administrators to investigate. It does not actively block or prevent the intrusion.

Features of IDS:

• Monitoring and Alerting:
  • Monitors network traffic or system activity for potential threats (e.g., anomalies, signatures of known attacks).
  • Sends alerts to security personnel for further analysis or manual action.
• Passive System:
  • Does not interfere with network traffic or block malicious activities.
• Detection Methods:
  • Signature-based Detection:
    • Matches traffic patterns against a database of known attack signatures.
  • Anomaly-based Detection:
    • Identifies deviations from normal network behavior that could indicate an attack.

Use Cases:

• Identifying ongoing attacks or suspicious behavior.
• Providing visibility into potential vulnerabilities or misconfigurations.

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2. Intrusion Prevention System (IPS)

An IPS builds upon the functionality of an IDS but goes a step further by actively blocking or preventing malicious activities. It sits in-line with network traffic, inspecting packets and taking automated action to mitigate threats.

Features of IPS:

• Monitoring and Prevention:
  • Inspects network traffic in real time and takes immediate actions, such as blocking IPs, dropping packets, or terminating connections.
• Active System:
  • Operates in-line, intercepting and analyzing traffic before it reaches its destination.
• Detection Methods:
  • Uses both signature-based and anomaly-based detection, similar to IDS.

Use Cases:

• Protecting critical systems from known attacks.
• Preventing exploitation of vulnerabilities in real time.

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Key Differences Between IDS and IPS

Feature	IDS	IPS
Primary Function	Detects and alerts on malicious activity	Detects and actively blocks malicious activity
Placement	Out-of-band (passive monitoring)	In-line (active traffic filtering)
Action	Alerts administrators	Blocks, drops, or mitigates threats
Impact on Traffic	No direct impact	Can delay or block network traffic
Responsiveness	Reactive (requires human intervention)	Proactive (automatic threat prevention)
Risk of False Positives	Alerts only (low operational risk)	May block legitimate traffic
Performance Overhead	Low (no in-line processing)	Moderate (in-line inspection adds overhead)

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When to Use IDS vs. IPS

Use IDS When:

• You need visibility into potential threats without disrupting traffic.
• Manual response and investigation are acceptable.
• You're in a monitoring phase or analyzing network behavior for security improvements.

Use IPS When:

• You need real-time, automated protection against threats.
• Blocking malicious activity is critical to maintaining security.
• You can manage the potential latency or false positives caused by in-line traffic inspection.