Open-Source Firewall OS: A Comprehensive Guide

A firewall OS is a specialized operating system designed to run on dedicated hardware, offering advanced tools to control and monitor network traffic. It enforces security policies, supports VPNs and intrusion detection, and is highly customizable for specific needs.

Here’s a list of open-source firewall OS options:

• pfSense – Based on FreeBSD, offering a robust firewall and routing platform.
• OPNsense – A fork of pfSense with a focus on security and usability.
• IPFire – Linux-based, with a strong emphasis on simplicity and security.
• Smoothwall – Designed for small to medium enterprises with web filtering.
• Untangle – Provides a user-friendly interface with modular security apps.

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You Should Know: Essential Firewall Commands & Configurations

pfSense/OPNsense (FreeBSD-Based)

• Check firewall rules:

  pfctl -sr
  

• Enable/disable firewall:

  pfctl -d  Disable 
  pfctl -e  Enable 
  

• View NAT rules:

  pfctl -sn
  

IPFire (Linux-Based)

• Start/stop firewall:

  systemctl start firewall 
  systemctl stop firewall 
  

• Check blocked IPs:

  grep BLOCK /var/log/messages 
  

General Linux Firewall (iptables/nftables)

• List all rules:

  iptables -L -n -v 
  nft list ruleset 
  

• Block an IP:

  iptables -A INPUT -s 192.168.1.100 -j DROP 
  

• Allow SSH only from a specific IP:

  iptables -A INPUT -p tcp --dport 22 -s 192.168.1.50 -j ACCEPT 
  iptables -A INPUT -p tcp --dport 22 -j DROP 
  

Windows Firewall (PowerShell)

• List all firewall rules:

  Get-NetFirewallRule | Format-Table -AutoSize 
  

• Block an IP:

  New-NetFirewallRule -DisplayName "Block Malicious IP" -Direction Inbound -RemoteAddress 192.168.1.100 -Action Block 
  

What Undercode Say

Firewalls are the first line of defense in network security. Open-source firewall OS options like pfSense, OPNsense, and IPFire provide powerful, customizable solutions for securing networks. Mastering firewall commands (iptables, pfctl, Windows Firewall) ensures granular control over traffic. Always monitor logs (/var/log/messages, Get-NetFirewallLog) and update rules regularly to adapt to threats.

Expected Output:

• Firewall rules applied successfully.
• Logs showing blocked/allowed traffic.
• Secure VPN tunnels and intrusion detection alerts.

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References:

Reported By: Xmodulo Open – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅

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