Setting Up Snort: Installing and Configuring Snort IDS -SecureMyOrg

By SecureMyOrg
on January 4, 2025

intrusion detection

Intrusion Detection Systems (IDS) are critical for securing modern networks. Among the popular open-source IDS tools, Snort stands out for its flexibility, community support, and effectiveness. In this blog, we’ll walk you through setting up Snort—from installation to configuration—to monitor and protect your network against potential threats.

What is Snort?

Snort is an open-source network intrusion detection and prevention system (IDS/IPS) developed by Cisco Systems. It works by analyzing network traffic in real-time, identifying suspicious activities, and alerting administrators. With its extensive library of rules, Snort can detect various threats, including malware, port scans, and unauthorized access attempts.

Key Features of Snort

Protocol Analysis: Monitors network protocols to detect anomalies.
Content Searching/Matching: Scans packet payloads for specific patterns.
Detection Engine: Uses rules to identify potential threats.
Real-Time Alerts: Provides instant notifications for detected intrusions.

Prerequisites for Setting Up Snort

Before diving into the installation, ensure you have the following:

Operating System: Snort is compatible with various platforms, including Linux (Ubuntu, CentOS) and Windows. For this guide, we’ll focus on Ubuntu.
Root Access: Administrative privileges are required to install and configure Snort.
Network Interface: A dedicated network interface card (NIC) for monitoring traffic is recommended.
Dependencies: Tools like gcc, make, libpcap, and libpcre are essential for compiling Snort.

Step 1: Installing Snort

Follow these steps to install Snort on Ubuntu:

1. Update the System

Update your system packages to ensure you have the latest dependencies:

bash

sudo apt update && sudo apt upgrade -y

2. Install Required Libraries

Snort relies on several libraries. Install them using the following command:

bash

sudo apt install -y build-essential libpcap-dev libpcre3-dev libdnet-dev zlib1g-dev

3. Download Snort

Download the latest Snort source code from the official website:

bash

wget https://www.snort.org/downloads/snort/snort-2.9.X.tar.gz

4. Extract and Compile

Extract the downloaded file and navigate to the Snort directory:

bash

tar -xvzf snort-2.9.X.tar.gz
cd snort-2.9.X

Compile and install Snort:

bash

./configure --enable-sourcefire
make
sudo
 make install

5. Verify Installation

Ensure Snort is installed by checking its version:

bash

snort -v

Step 2: Configuring Snort

With Snort installed, the next step is to configure it for your network environment.

1. Set Up Configuration Files

Snort’s configuration file, snort.conf, is located in /etc/snort. If it’s not present, create the directory and move the default configuration file:

bash

sudo mkdir /etc/snort
sudo cp /usr/local/etc/snort/snort.conf /etc/snort/

2. Define Network Variables

Edit snort.conf to specify your network settings. Open the file with a text editor:

bash

sudo nano /etc/snort/snort.conf

Modify the following variables:

HOME_NET: Define the IP range of your internal network, e.g., 192.168.1.0/24.
EXTERNAL_NET: Set this to any traffic outside your network, typically !HOME_NET.

bash

var HOME_NET 192.168.1.0/24
var EXTERNAL_NET !$HOME_NET

3. Enable Rule Sets

Snort rules are the heart of its detection capability. Download and place rule sets in the /etc/snort/rules directory. To enable a rule, uncomment or add its path in snort.conf:

bash

include $RULE_PATH/local.rules
include $RULE_PATH/community.rules

4. Create a Logging Directory

Specify where Snort should log detected events:

bash

sudo mkdir /var/log/snort
sudo chmod -R 755 /var/log/snort

Update snort.conf to point to this directory:

bash

output alert_fast: /var/log/snort/alerts

Step 3: Running Snort

Once configured, you can run Snort in different modes:

1. Test Configuration

Before starting Snort, test its configuration for errors:

bash

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

2. Run Snort in IDS Mode

To monitor traffic and log alerts:

bash

sudo snort -c /etc/snort/snort.conf -i eth0

Replace eth0 with the appropriate network interface.

3. Analyze Logs

Snort logs events in /var/log/snort. Use tools like grep or custom scripts to analyze alerts:

bash

cat /var/log/snort/alerts

Best Practices for Snort Configuration

Regular Updates: Keep Snort and its rule sets updated to protect against new threats.
Rule Customization: Modify existing rules or create custom rules tailored to your environment.
Testing: Regularly test configurations to ensure Snort functions as expected.
Integration: Combine Snort with other tools like SIEMs for comprehensive threat management.

A well-configured Snort setup is an essential layer of defense for any network. By adhering to these best practices, you can maximize Snort’s efficiency and ensure a proactive approach to network security.

Conclusion

Setting up Snort as an IDS is a cost-effective way to enhance your network security. By following this guide, you’ll have a robust system capable of detecting and alerting you to potential intrusions. Regularly update and fine-tune your Snort configuration to stay ahead of emerging threats.

For more advanced use cases, consider exploring Snort’s IPS capabilities or integrating it with visualization tools for better insights. A secure network starts with proactive measures, and Snort is an excellent tool to have in your arsenal.

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At SecureMyOrg, we uncover and fix all possible security vulnerabilities of mobile and web, while providing solutions to mitigate risks. We are trusted by renowned companies like Yahoo, Gojek and Rippling, and with 100% client satisfaction, you’re in safe hands!

Some of the things people reach out to us for –

Building their cybersecurity program from scratch – setting up cloud security using cost-effective tools, SIEM for alert monitoring, building policies for the company
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