Securing your Network with Snort

Securing your network with Snort is a powerful way to detect and prevent threats in real-time. Snort is an open-source network intrusion detection system (NIDS) and intrusion prevention system (NIPS) that analyzes network traffic for malicious activity.

Below is a comprehensive guide on how to secure your network using Snort , including installation, configuration, rule management, and integration options.

🔐 What is Snort?

Snort is often referred to as the “Swiss Army Knife” of network security monitoring. It works by capturing packets, analyzing them against a set of rules, and generating alerts or blocking traffic when suspicious behavior is detected.

Key Features:

Real-time traffic analysis
Protocol inspection
Content matching (via signatures)
Detection of known attacks (buffer overflows, stealth port scans, etc.)
Can be used in inline mode for active prevention

🛠️ Prerequisites for Installing Snort

Before installing Snort, ensure you have:

Requirement	Description
Operating System	Linux (Ubuntu, CentOS, etc.) recommended
Hardware	At least 2GB RAM, 1 CPU core (more for high-traffic environments)
Network Interface	In promiscuous mode or mirrored port (for passive monitoring)
Tools Installed	`libpcap-dev`,`bison`,`flex`,`gcc`,`make`,`libnetfilter-queue-dev`(for IPS)

📦 Installation Steps (Ubuntu Example)

Step 1: Install Dependencies

sudo apt update

sudo apt install -y build-essential libpcap-dev libpcre3-dev libssl-dev pkg-config

Step 2: Download and Install Snort

You can install from source or use packages. Here’s building from source:

cd /tmp

wget https://www.snort.org/downloads/snort/daq-2.0.7.tar.gz

wget https://www.snort.org/downloads/snort/snort-2.9.20.tar.gz

tar -xvzf daq-2.0.7.tar.gz

cd daq-2.0.7

./configure && make && sudo make install

cd ..

tar -xvzf snort-2.9.20.tar.gz

cd snort-2.9.20

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

Step 3: Set Up Configuration Files

sudo mkdir -p /etc/snort /etc/snort/rules

sudo cp etc/*.conf* /etc/snort

sudo cp etc/schema.sql /etc/snort

Step 4: Configure Basic Rules

Edit /etc/snort/snort.conf:

Set HOME_NET to your internal network range
Set EXTERNAL_NET to !$HOME_NET
Point to local rule files:bash1include $RULE_PATH/local.rules

Create a basic test rule in /etc/snort/rules/local.rules:

alert tcp any any -> $HOME_NET80 (msg:”HTTP Traffic Detected”; sid:1000001; rev:1;)

🧪 Run Snort in IDS Mode

To test Snort in detection-only mode:

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

This will print alerts to the console whenever HTTP traffic is detected.

🔒 Enable Intrusion Prevention (IPS Mode)

To drop malicious traffic in real-time, run Snort in inline mode using NFQUEUE :

Step 1: Set up iptables redirect

sudo iptables -I FORWARD -j NFQUEUE –queue-num 0

Step 2: Run Snort in Inline Mode

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

Make sure you have rules with drop actions instead of alert.

Example drop rule:

drop tcp any any -> $HOME_NET23 (msg:”Blocking Telnet”; sid:1000002; rev:1;)

📚 Rule Management

Snort uses rules to detect threats. You can manage rules via:

1. Community Rules

Snort Community Rules (free, registration required)

2. Snort Subscriber Rules

Paid subscription with faster updates and more coverage

3. Custom Rules

Write your own based on network behavior and policies.

Tip: Use tools like PulledPork to automate rule updates.

📊 Logging & Alerting

By default, Snort logs to /var/log/snort. You can configure it to log to:

Database : MySQL, PostgreSQL (use Barnyard2 or Suricata for processing)
SIEM Integration : Forward logs to Splunk, ELK Stack, Graylog, etc.
Syslog : Send alerts to centralized logging systems

🧰 Additional Tools for Better Visibility

Tool	Purpose
Barnyard2	Processes unified2 binary logs into databases or syslog
Suricata	Alternative NIDS with similar syntax and features
Snorby / ELSA / Squert	Web-based dashboards for Snort alerts
ELK Stack	Centralized log analysis and visualization

🧩 Integration with Other Security Systems

Firewalls : Integrate with iptables, nftables, or PF for automated blocking
SOAR Platforms : Trigger workflows on alert
Threat Intelligence Feeds : Import IP/domain blacklists into Snort rules
OpenZiti Integration (Bonus) :
- Use Snort to monitor Ziti overlay network traffic for anomalies
- Deploy Snort at edge routers where Ziti connects external clients

✅ Best Practices for Securing Your Network with Snort

Use Layered Defense : Combine Snort with firewalls, endpoint protection, and SIEMs.
Keep Rules Updated : Regularly fetch new threat intelligence rules.
Monitor Logs Daily : Use automation and dashboards to spot trends.
Tune Rules : Reduce false positives by customizing rules to your environment.
Run in Test Mode First : Start with IDS before enabling IPS/drop rules.
Secure Snort Itself : Protect Snort hosts with strong access controls.

📄 Sample Output (Alert)

[**] [1:1000001:1] HTTP Traffic Detected [**]

[Priority: 0]

04/05-10:20:12.345678 192.168.1.100:54321 -> 192.168.1.200:80

TCP TTL:64 TOS:0x0 ID:54321 IpLen:20 DgmLen:1500 DF

***AP*** Seq: 0x12345678 Ack: 0x87654321 Win: 0x3FD TcpLen: 20

📌 Summary Checklist

Task	Status
Install Snort	✅
Configure Interfaces	✅
Set Up Rules	✅
Choose IDS or IPS Mode	✅
Enable Logging	✅
Integrate with SIEM or Dashboard	✅
Schedule Rule Updates	✅