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Intrusion Detection

Intrusion Detection – Detailed Explanation

Introduction

Intrusion Detection is the process of monitoring computer systems and networks to detect unauthorized access, misuse, or attacks.

👉 “Intrusion Detection = Identify suspicious activities in a system/network.”

It plays a vital role in Information Security by helping detect attacks early and respond quickly.

1. Intruders

Definition

An Intruder is a person or entity that tries to gain unauthorized access to a system or network.

Types of Intruders

1. Masquerader (Outsider)

  • Unauthorized user pretending to be legitimate

📌 Example: Hacker using stolen credentials

2. Misfeasor (Insider)

  • Authorized user misusing privileges

📌 Example: Employee accessing restricted data

3. Clandestine User

  • Gains control and hides activities

📌 Most dangerous type

Characteristics of Intruders

  • Attempt unauthorized access
  • Exploit vulnerabilities
  • Hide their activities
  • Steal or modify data

2. Intrusion Detection

Definition

Intrusion Detection is the process of:

  • Monitoring system activities
  • Identifying suspicious behavior
  • Alerting administrators

Types of Detection Methods

1. Signature-Based Detection

  • Detects known attack patterns

📌 Fast but cannot detect new attacks

2. Anomaly-Based Detection

  • Detects abnormal behavior

📌 Can detect unknown attacks

3. Hybrid Detection

  • Combination of both methods

Functions of Intrusion Detection System (IDS)

  • Monitor system/network activity
  • Detect suspicious behavior
  • Generate alerts
  • Log security events

3. Host-Based Intrusion Detection System (HIDS)

Definition

A Host-Based IDS (HIDS) monitors activities on a single computer (host).

Features

  • Monitors system logs
  • Tracks file changes
  • Detects unauthorized access
  • Works on individual machines

Working

  1. Collects system data (logs, files)
  2. Analyzes activities
  3. Detects anomalies or attacks
  4. Generates alerts

Advantages

  • Detects internal attacks
  • Detailed system monitoring
  • Works even without network

Limitations

  • Limited to one host
  • Resource consumption
  • Difficult to manage at scale

4. Distributed Host-Based Intrusion Detection System (D-HIDS)

Definition

A Distributed HIDS is a system where multiple host-based IDS are connected and managed centrally.

Features

  • Monitors multiple hosts
  • Centralized control
  • Correlates data from different systems

Working

  1. Each host collects data
  2. Data sent to central server
  3. Central system analyzes patterns
  4. Alerts generated for threats

Advantages

  • Scalable
  • Better attack detection
  • Centralized monitoring

Limitations

  • Complex setup
  • Network dependency
  • Higher cost

5. Network-Based Intrusion Detection System (NIDS)

Definition

A Network-Based IDS (NIDS) monitors network traffic to detect suspicious activities.

Features

  • Monitors packets in network
  • Detects attacks in real-time
  • Covers multiple systems

Working

  1. Captures network traffic
  2. Analyzes packets
  3. Matches patterns or anomalies
  4. Generates alerts

Advantages

  • Monitors entire network
  • Detects external attacks
  • Real-time detection

Limitations

  • Cannot detect encrypted traffic easily
  • May miss internal attacks
  • High-speed networks are challenging

Comparison: HIDS vs NIDS vs D-HIDS

FeatureHIDSNIDSD-HIDS
ScopeSingle hostNetworkMultiple hosts
DetectionInternalExternalBoth
ManagementLocalCentralCentralized
ComplexityLowMediumHigh

Intrusion Detection and CIA Triad

  • Confidentiality → Detect data breaches
  • Integrity → Detect unauthorized changes
  • Availability → Detect DoS attacks

Intrusion Detection in Cyber Law (India)

Under IT Act, 2000:

  • Section 43 → Unauthorized access
  • Section 66 → Cyber offences

📌 IDS helps organizations comply with security regulations.

Real-Life Examples

  • Detecting unauthorized login attempts
  • Identifying malware activity
  • Monitoring suspicious network traffic

Advantages of Intrusion Detection

  • Early attack detection
  • Improves security
  • Helps in incident response
  • Supports auditing

Limitations

  • False positives
  • Requires skilled management
  • Cannot prevent attacks (only detects)

Conclusion

Intrusion Detection is a critical security mechanism that helps identify unauthorized activities in systems and networks. By using HIDS, NIDS, and Distributed IDS, organizations can effectively monitor and respond to cyber threats, ensuring better protection of digital assets.

📘 MCA Exam Tip

For 10–15 marks:

  • Define intruders
  • Explain IDS
  • Cover HIDS, NIDS, D-HIDS
  • Add comparison table
  • Include advantages + limitations