334.2 Network Intrusion Detection (weight: 4)

Tech Tutorial: 334.2 Network Intrusion Detection (weight: 4) #

In this tutorial, we will delve into the realm of network intrusion detection, focusing on the key knowledge areas relevant to the exam objective 334.2. Understanding and implementing effective network intrusion detection strategies are critical to maintaining the security and integrity of network infrastructures.

Introduction #

Network Intrusion Detection Systems (NIDS) are essential tools that help in monitoring network traffic for suspicious activities and potential threats. They analyze traffic to detect signs of malicious activities or policy violations. This tutorial will cover popular utilities like Snort and Bro (now known as Zeek), which are commonly used for network intrusion detection.

Key Knowledge Areas: #

  • Installation and configuration of Snort
  • Basic operation of Snort
  • Understanding, writing, and maintaining rules in Snort
  • Installation and configuration of Bro/Zeek
  • Basic operation of Bro/Zeek
  • Understanding, writing, and maintaining scripts in Bro/Zeek

Utilities: #

  • snort
  • zeek

Step-by-Step Guide #

1. Installation and Configuration of Snort #

Installation: #

Snort is available from its official website or can be installed through package managers. For Debian-based systems:

sudo apt update
sudo apt install snort

For Red Hat-based systems:

sudo yum install snort

Configuration: #

After installation, configure Snort by editing its configuration file:

sudo nano /etc/snort/snort.conf

You need to set up the network variables to reflect your environment:

ipvar HOME_NET 192.168.1.0/24
ipvar EXTERNAL_NET !$HOME_NET

Testing the Configuration: #

To test if Snort is set up correctly:

sudo snort -T -c /etc/snort/snort.conf

2. Basic Operation of Snort #

To run Snort in network intrusion detection mode with console output:

sudo snort -q -A console -i eth0 -c /etc/snort/snort.conf

Replace eth0 with your network interface.

3. Snort Rules #

Rules in Snort are written in a straightforward format that specifies what to look for and what to do when it finds it. Here is an example of a simple rule:

alert tcp $EXTERNAL_NET any -> $HOME_NET 443 (msg:"Possible SSL Traffic"; sid:1000001; rev:1;)

To add this rule, append it to /etc/snort/rules/local.rules and restart Snort.

4. Installation and Configuration of Bro/Zeek #

Installation: #

Install Zeek from the official repository:

sudo apt install zeek

Configuration: #

Edit the main configuration file to adjust settings:

sudo nano /usr/local/zeek/etc/node.cfg

Set appropriate network interface:

[zeek]
type=standalone
host=localhost
interface=eth0

5. Basic Operation of Bro/Zeek #

To run Zeek in real-time mode:

sudo zeekctl deploy

This command checks the configuration, starts Zeek, and keeps it running.

6. Bro/Zeek Scripts #

Scripts in Zeek allow for complex event handling. Here’s an example of a script that logs HTTP GET requests:

event http_request(c: connection, method: string, original_URI: string) {
    if (method == "GET") {
        print fmt("GET request observed: %s", original_URI);
    }
}

Save this script as http_get.zeek and load it by modifying local.zeek:

@load ./http_get

Conclusion #

Effective use of tools like Snort and Zeek is crucial for network security. This tutorial provided an introduction to setting up and using these tools for intrusion detection. Mastery of these tools requires continuous learning and practical application, so keep practicing and stay updated with the latest in cybersecurity.

Remember, the security of your network infrastructure depends significantly on proactive measures and the effective detection of potential threats. Happy securing!