NISGTC Network Security Labs – Lab 9: Intrusion Detection Using Snort

In the ever-evolving world of cybersecurity, protecting networks from malicious attacks is a paramount concern for organizations. Intrusion Detection Systems (IDS) are vital components of network security, helping detect and mitigate unauthorized access and other malicious activities in real-time. In this article, we’ll delve into Lab 9: Intrusion Detection Using Snort, a key lab in the NISGTC (National Institute for Smart Government and Technology) Network Security Labs series.

Introduction to Intrusion Detection Systems (IDS)

An Intrusion Detection System (IDS) is designed to monitor network traffic for suspicious activities, alert administrators, and in some cases, actively block attacks. IDS solutions help protect systems by detecting unauthorized access, malicious actions, or policy violations. There are two main types of IDS:

• Network-based IDS (NIDS): Monitors network traffic and detects suspicious activities over the network.
• Host-based IDS (HIDS): Monitors the activities on individual devices, including file access, system calls, and user activity.

In Lab 9 of the NISGTC Network Security Labs series, the focus is on using Snort, an open-source network-based IDS, to detect intrusions and malicious activities in a network environment.

Understanding Snort

Snort is one of the most widely used open-source network intrusion detection systems (NIDS). It was developed by Martin Roesch in 1998 and has since become a staple in network security due to its flexibility, ease of use, and strong community support. Snort performs deep packet inspection, logs suspicious activity, and generates alerts based on predefined or custom rules.

Snort can operate in three modes:

• Sniffer Mode: Captures network packets and displays them.
• Packet Logger Mode: Logs network traffic to a file for later analysis.
• Network Intrusion Detection Mode: Analyzes network traffic and generates alerts based on patterns of suspicious behavior or attacks.

Setting Up Snort for Intrusion Detection

Before diving into the practical aspects of using Snort, it’s important to set up and configure the tool correctly. Below is a step-by-step guide to configuring Snort for intrusion detection:

Step 1: Install Snort

Snort can be installed on various operating systems, including Linux, Windows, and macOS. In a typical NISGTC Network Security Lab setup, Snort is usually installed on a Linux-based virtual machine or server.

To install Snort on a Debian-based system (like Ubuntu), use the following command:

Step 2: Configure Snort

Once installed, the next step is to configure Snort. The main configuration file for Snort is snort.conf, which specifies the settings for network interfaces, rulesets, and logging. Common configurations include:

• Defining the network interfaces Snort should monitor.
• Specifying the rule sets Snort should use for intrusion detection.
• Configuring logging and alerting mechanisms to capture detected intrusions.

The configuration file can be edited using any text editor:

Step 3: Download Snort Rules

To detect a wide range of network-based attacks, Snort relies on a set of predefined rules that define patterns of known threats. These rules need to be downloaded and updated regularly.

You can download the latest Snort rule set from the official Snort website or use the following command to update the rules:

Step 4: Start Snort in IDS Mode

After configuring Snort and ensuring the rules are up-to-date, Snort can be started in IDS mode to monitor network traffic in real-time.

To run Snort in IDS mode, use the following command:

Where:

• -A console specifies that alerts will be displayed in the console.
• -c /etc/snort/snort.conf points to the configuration file.
• -i eth0 specifies the network interface Snort will monitor (replace eth0 with the correct interface name).

Detecting Intrusions Using Snort

Once Snort is up and running, it will start analyzing network traffic and generating alerts based on the rules defined in the configuration file. These alerts may include:

• Port scans: Unauthorized attempts to probe various ports.
• Denial of Service (DoS): Malicious attempts to flood a network or system with traffic.
• Signature-based attacks: Attacks that match known signatures, such as buffer overflows, SQL injections, or exploits of specific vulnerabilities.

For example, if Snort detects an SQL injection attempt, it will trigger an alert, logging the attack and providing valuable information for network administrators to investigate further.

Analyzing Alerts and Logs

Snort can generate detailed alerts and logs whenever suspicious activity is detected. These logs provide insight into the nature of the attack, the source and destination of malicious traffic, and the specific rule that triggered the alert.

The logs can be reviewed in real-time on the console or stored in log files for later analysis. Logs are typically stored in the /var/log/snort/ directory.

For example, a log entry might look like this:

This entry indicates that Snort detected an SQL Injection Attempt coming from IP address 192.168.1.100 targeting 192.168.1.200 on port 80.

6. Real-World Applications of Snort in Network Security

Using Snort for intrusion detection has numerous real-world applications:

• Early Detection of Attacks: Snort allows administrators to detect intrusions in their network before they cause significant damage.
• Compliance: Snort helps organizations comply with regulatory standards such as PCI DSS, HIPAA, and GDPR by monitoring and logging network traffic.
• Forensic Analysis: In the event of a security breach, Snort logs and alerts can provide valuable data for forensic investigations and root cause analysis.

Challenges and Limitations

While Snort is a powerful tool for intrusion detection, it does have certain challenges:

• Performance: Snort can consume a significant amount of system resources, especially in high-traffic environments.
• False Positives: Like any IDS, Snort may generate false positives, triggering alerts for benign activity that resembles an attack.
• Complex Configuration: Setting up Snort with the correct rules and configuration requires expertise and thorough testing.

Conclusion

Lab 9: Intrusion Detection Using Snort in the NISGTC Network Security Labs provides hands-on experience with one of the most widely used IDS tools in the cybersecurity industry. By using Snort to monitor and protect a network, students and professionals gain valuable insights into how intrusion detection systems work and how to defend against common cyber threats. With Snort’s real-time monitoring capabilities, network administrators can detect attacks early, protect their systems, and ensure the security and integrity of their networks.

The knowledge gained from this lab is a vital skill set for anyone pursuing a career in network security, making Snort an essential tool in the modern cybersecurity landscape.