Situational Awareness and Intrusion Detection – Part 1

Introduction

In modern cybersecurity, preventative security measures such as authentication, access control, and security policies aim to protect systems from attacks. However, when an attack bypasses these defenses, intrusion detection and prevention systems (IDS and IPS) become critical for identifying and mitigating threats.

This article explores the fundamental principles of intrusion detection systems (IDS) and intrusion prevention systems (IPS), their classifications, and their roles in cybersecurity.

Understanding IDS and IPS

Intrusion Detection Systems (IDS)

An IDS is a combination of hardware and software designed to collect and analyze network traffic to detect suspicious activities. IDS solutions use various sensors to monitor:

  • Network packets
  • System logs
  • Application behavior

IDSs can be either:

  1. Host-based (HIDS): Installed on individual devices to monitor local activities.
  2. Network-based (NIDS): Monitors network traffic for potential threats.

Intrusion Prevention Systems (IPS)

An IPS actively responds to detected threats, unlike an IDS, which primarily reports alerts. The IPS can take direct actions, such as:

  • Blocking malicious IP addresses
  • Aborting suspicious processes
  • Shutting down affected systems

Active vs. Passive Defenses

  • Passive defenses (IDS): Monitor activity and generate alerts but do not take action.
  • Active defenses (IPS): Respond to threats in real time by blocking or mitigating attacks.

Both systems do not engage in offensive cybersecurity tactics and only operate within their security domain.

Key Components of IDS and IPS

A typical IDS/IPS workflow consists of:

  1. Audit subsystem: Captures system activity logs.
  2. Analysis component: Uses statistical or pattern-based methods to detect anomalies.
  3. Response mechanism: Generates alerts or takes action to mitigate threats.

Severity Levels of Alerts

Alerts generated by IDS/IPS are often categorized as:

  • High severity: Critical attacks like buffer overflow exploits
  • Medium severity: Potential reconnaissance activity
  • Low severity: Suspicious but not necessarily malicious behavior

Host-Based IDS and IPS (HIDS/HIPS)

Functionality

Host-based solutions are installed on individual systems and monitor:

  • Login failures and software crashes
  • System file integrity
  • Running processes and network connections

A specialized form of host-based intrusion detection is application-level IDS, which focuses on monitoring SQL queries to prevent SQL injection attacks.

Advantages of Host-Based IDS/IPS

✅ Not affected by network encryption
✅ Granular and precise detection
✅ Effective against insider threats

Disadvantages of Host-Based IDS/IPS

❌ Consumes system resources
❌ Limited to the monitored device
❌ Can be disabled by skilled attackers

Network-Based IDS and IPS (NIDS/NIPS)

Functionality

Network-based detection systems are deployed at strategic points within the network infrastructure, such as:

  • Routers
  • Gateways
  • Switches

These systems analyze traffic patterns and can detect:

  • Port scans and attack payloads (inbound monitoring)
  • Malware-infected outbound traffic (outbound monitoring)

Advantages of Network-Based IDS/IPS

✅ Fully passive monitoring (invisible to attackers)
✅ Does not consume host system resources
✅ Can analyze traffic from multiple devices

Disadvantages of Network-Based IDS/IPS

❌ Requires packet reassembly, increasing overhead
❌ Limited in detecting host-specific threats
❌ Encrypted traffic appears scrambled

Combining Host-Based and Network-Based Solutions

HIDS and NIDS are complementary solutions, offering a multi-layered security approach. While network-based IDS can detect anomalies in network traffic, host-based solutions can identify internal system threats.

However, managing multiple IDS/IPS solutions requires dedicated resources for:

  • Configuration
  • Monitoring
  • Incident response

Automation is improving IDS/IPS efficiency, but human expertise remains essential in cybersecurity operations.

Conclusion

Intrusion detection and prevention systems play a crucial role in modern cybersecurity. While IDS provides passive monitoring, IPS actively mitigates threats. Deploying a combination of host-based and network-based solutions ensures comprehensive security coverage.

In the next part of this series, we will explore detection mechanisms, including signature-based and anomaly-based detection, to further understand how IDS/IPS operate in real-world scenarios.

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