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What are the security features of pfSense and OPNSense?

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Strong security measures are essential for today’s computer networks due to the increasing number of potential vulnerabilities. Both pfSense and OPNsense, which are based on FreeBSD, have become popular options for many network administrators. To protect against a wide range of cyber threats and to guarantee the privacy, integrity, and accessibility of data, these open-source firewall solutions provide a wealth of security options. Below, we explore some of their key security features:

  • Stateful Firewall
  • VPN (Virtual Private Network) Support
  • Intrusion Detection and Prevention System (IDS/IPS)
  • Traffic Shaping and Quality of Service (QoS)
  • DNS Filtering
  • Web Proxy and Filtering
  • VLAN Support

Stateful Firewall

A stateful firewall is a firewall that tracks the state of connections between devices on a network. This allows the firewall to know which connections are allowed and which ones are not. This is in contrast to a stateless firewall, which only looks at the source and destination IP addresses and ports of packets.

Both PfSense and OPNSense use Stateful Packet Inspection (SPI) to track and filter network connections. SPI is an advanced firewall technique that tracks the state of network connections and only allows traffic that is part of an established connection. This helps prevent unauthorized access to the network and ensures that only legitimate traffic is allowed through the firewall.

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Both PfSense and OPNSense use the same underlying stateful firewall Both PfSense and OPNSense utilize the same underlying stateful firewall technology, which is based on FreeBSD’s firewall framework, enabling users to create rules that govern allowed and blocked connections while supporting state tracking for TCP, UDP, and ICMP protocols.

PfSense offers a more granular and customizable stateful firewalling approach, allowing users to define specific connection rules, while OPNSense provides a simplified and user-friendly option, suitable for those with less experience in firewall management.

OPNSense groups firewall rules by category, which is especially useful for more demanding network setups.

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Both OPNsense and pfSense utilize the same underlying stateful firewall technology based on FreeBSD’s firewall framework. Nevertheless, pfSense provides a stateful firewalling technique that is more comprehensive and adaptable, letting users create unique rules for each connection. OPNsense, on the other hand, is a streamlined and user-friendly alternative that works well for people with little expertise in managing firewalls. Consequently, pfSense is a superior alternative if you require a firewall with greater flexibility and fine-grained control.

VPN (Virtual Private Network) Supports

A virtual private network (VPN) is a secure connection between two or more devices over a public network, such as the Internet. VPNs are often used to allow users to securely access remote networks, such as their work network, from home or another location.

Both pfSense and OPNSense support a wide range of VPN protocols, including OpenVPN, IPsec, L2TP/IPsec, PPTP, and WireGuard. They support a variety of VPN features, such as split tunneling, multi-user VPNs, and site-to-site VPNs.

OPNsense, on the other hand, offers a VPN solution that is easier to set up and may therefore appeal to users with less technical expertise.

OPNsense offers a wide range of VPN technologies, ranging from modern SSL VPNs to well-known IPsec, as well as WireGuard and Zerotier via plugins.

Both OPNsense and pfSense support a wide range of VPN protocols and features. However, OPNsense’s VPN solution may be more appealing to users with less technical knowledge due to its simpler setup. So, if you prioritize simplicity in VPN setup, OPNsense could be more suitable.

Intrusion Detection and Prevention System (IDS/IPS)

An intrusion detection system (IDS) is a system that monitors network traffic for malicious activity. An intrusion prevention system (IPS) is a system that monitors network traffic for malicious activity and takes action to block it.

When it comes to detecting malicious activity on networks, both pfSense and OPNsense are useful because they support IDS/IPS functionality. Both use the robust and flexible Snort IDS/IPS engine to monitor networks for malicious activity.

OPNsense’s built-in support for Emerging Threats rules simplifies the setup and management of rule categories and allows for automatic updates to be performed at predetermined intervals, thereby enhancing network security.

However, pfSense uses a packet analyzer based on the open-source project Snort to perform intrusion detection and prevention functions. It uses Layer 7 application detection and maintains an up-to-date database of emerging threats to better identify potential dangers.



  • Firewall
  • Stateful Packet Inspection (SPI)
  • GeoIP blocking
  • Anti-spoofing
  • Time-based rules
  • Connection rules
  • Dynamic DNS
  • Reverse proxy
  • Captive portal guest network
  • Concurrent IPv4 and IPv6 support
  • NAT mapping (inbound/outbound)
  • VLAN support (802.1q)
  • Configurable static routing
  • IPv6 network prefix translation
  • IPv6 router advertisements
  • Multiple IP addresses per interface
  • DHCP server
  • DNS forwarding
  • Wake-on-LAN
  • PPPoE server
  • Reporting and monitoring
  • Web-based interface
  • Local and remote logging
  • SNMP monitoring
  • Notifications via web interface, SMTP, or Growl
  • Hardware monitoring
  • Networking diagnostic tools

In addition to the above features, pfSense also includes a number of add-on packages that can be installed to extend its functionality. Some popular add-on packages include:

  • Suricata: Intrusion detection and prevention system
  • HAProxy: Load balancer
  • SquidGuard: Web content filter
  • OpenVPN: VPN server
  • Snort: Intrusion detection system

pfSense is a powerful and versatile firewall and router software that can be used to protect and manage networks of all sizes.


  • Engine used
  • Snort
  • Snort/Suricata
  • Protocols supported
  • IP, TCP, UDP, and ICMP
  • IP, TCP, UDP, and ICMP
  • Features supported
  • Detection, prevention, and alerting
  • Detection, prevention, and alerting
  • Granularity of configuration
  • More granular
  • Less granular
  • Ease of configuration
  • More complex
  • Easier

Both OPNsense and pfSense support IDS/IPS functionality using the Snort IDS/IPS engine. Support for Emerging Threats rules out of the box in OPNsense streamlines rule maintenance and provides automated rule changes. PfSense’s packet analyzer, Snort, keeps track of new security risks so that you may see them sooner. Both are skilled in this field; thus, the deciding element may lie elsewhere.

Traffic Shaping and Quality of Service (QoS)

Traffic shaping is a technique used to control the flow of network traffic. It can be used to prioritize certain types of traffic, such as voice or video traffic, to ensure that they receive the best possible performance.

QoS (Quality of Service) is a broader term that encompasses traffic shaping as well as other techniques for managing network traffic. QoS can be used to ensure that all types of traffic receive a certain level of service, regardless of the amount of traffic on the network.

Traffic shaping and Quality of Service (QoS) are essential features of pfSense that allow users to prioritize and control network traffic, ensuring critical services receive the necessary bandwidth. pfSense offers several traffic shaping mechanisms, including CBQ, PRIQ, and HFSC, which enable users to allocate bandwidth and prioritize traffic based on different criteria. The implementation of traffic shaping is achieved through shaper queues, where each queue is assigned specific bandwidth and priority settings, giving users control over traffic flow and resource allocation.

To determine which traffic receives priority in each queue, users can configure assignment rules, tailoring the treatment of various traffic types to guarantee adequate bandwidth for critical services. Furthermore, pfSense employs the ALTQ framework for traffic shaping, which is closely integrated with network card drivers, enabling support for different schedulers and queue layouts. In addition, pfSense provides Limiters, allowing users to define maximum bandwidth limits for specific types of traffic. For simplified QoS configuration in common scenarios, pfSense offers a user-friendly Traffic Shaping Wizard, enabling quick setup based on predefined profiles or custom rules for more complex requirements.

pfSense has many ways to shape traffic, giving users more control over resource allocation and priority. It also has a convenient Traffic Shaping Wizard that makes configuring QoS a breeze. For more strict filtering options, however, OPNsense uses DNS filtering and incorporates NextDNS. pfSense may be the best choice if sophisticated traffic shaping and QoS features are essential.

DNS Filtering

DNS filtering is a technique used to block access to malicious or unwanted websites. It works by redirecting DNS requests for those websites to a sinkhole, which is a server that does not resolve the DNS request.

OPNsense employs DNS filtering via the rules of its firewall and the DNS resolver. Unbound is a DNS resolver that verifies and caches DNS queries for the local network, allowing users to enable DNS filtering.

For even more stringent DNS filtering, users can integrate NextDNS into their OPNsense firewall setup. Better filtering and management of website content is now possible.

Additionally, OPNsense’s built-in proxy system enables category-based web filtering that can be combined with freely available or commercial blacklists. Together, they add a granular level of control and protection by letting users filter the web based on predefined categories.

OPNsense’s DNS filtering entails establishing the Unbound DNS resolver, integrating NextDNS for more sophisticated filtering options, and employing category-based web filtering via the built-in proxy system and applicable blacklists. This combination helps enhance network security and content control.

pfSense provides robust DNS filtering options via a variety of channels. Installing the pfBlockerNG plugin on pfSense enables users to efficiently block unwanted domains and IP ranges via DNS-based filtering.

The DNS Resolver or DNS Forwarder on pfSense can also be used to resolve DNS requests from local clients if pfSense is set up to prevent DNS queries from clients outside the local network. With this setup, DNS traffic can be managed and protected more effectively. Whitelists and blacklists in pfBlockerNG allow users to tailor their filtering policies by allowing or disabling access to only certain domains or IP addresses.

When combined, pfSense’s DNS filtering features—such as pfBlockerNG, client DNS query blocking, whitelisting, blacklisting, and IP filtering with DNS blackholing—give users the freedom to take charge of DNS security on their networks and adjust settings as needed.

Both OPNsense and pfSense offer DNS filtering options. For more advanced filtering, NextDNS may be integrated into OPNsense and used in tandem with the firewall rules and the DNS resolver. The pfBlockerNG plugin for PfSense is a powerful DNS filter that allows users to effectively block malicious domains and IP ranges. If DNS filtering is important, the choice may come down to personal preference or practical considerations, as both solutions offer robust functionality.

Web Proxy and Filtering

OPNsense provides comprehensive web filtering proxy features, empowering users to effectively control and manage web content. With category-based web filtering, users can utilize the built-in proxy and freely available or commercial blacklists to block undesirable websites.

The proxy settings are configurable, and authentication can be disabled, streamlining the web filtering setup.

OPNsense offers flexibility in customizing blacklist settings, allowing users to specify which website categories to block, with support for various blacklists like and

The transparent proxy mode automatically diverts all traffic to the proxy through Network Address Translation (NAT), simplifying the process without requiring client browser configurations. Additionally, setting up a transparent SSL/HTTPS proxy is possible by creating a Certificate Authority (CA) and configuring SSL settings, ensuring even encrypted traffic is comprehensively filtered.

Moreover, for advanced proxy control beyond the built-in features, users can explore plugins like Zenarmor, which provide extended capabilities not included in the default installation. This combination of built-in tools and plugins equips users with a versatile and robust set of options to efficiently manage and secure their web traffic.

OPNsense offers powerful web filtering proxy capabilities, including filtering based on category, allowing customers to have complete control over the websites their users access. It works with add-ons, such as Zenarmor, to increase its functionality. Those who want a built-in, user-friendly solution may find OPNsense more suitable if web filtering and proxy functions are essential.

VLAN Support

Using VLANs, a single switch may serve the same purpose as several separate switches by transporting numerous independent broadcast domains. Similar to how several switches may be used to segment a network, virtual local area networks (VLANs) can be used to isolate hosts on a single network segment. Devices on the same segment might be located on different switches thanks to trunking between them. If a device is trunking-capable, it can talk to others on different virtual LANs using a single physical connection.

VLAN routing is possible with pfSense. Using VLANs, a single switch may serve as if it were several by transporting numerous independent broadcast domains. You can set up virtual local area networks (VLANs) with pfSense by defining the VLANs on the pfSense interface and the VLAN settings on your networking gear.

OPNsense supports Virtual Local Area Networks (VLANs), which enables you to divide a single physical network into numerous smaller networks. ISP-issued IPTV devices frequently employ this segmentation for the QoS benefits it provides.

With OPNsense’s Virtual Local Area Network (VLAN) features, you can efficiently segment your local network’s traffic and set up standalone networks for things like Internet of Things (IoT) devices or guests.

Both OPNsense and pfSense support VLANs, allowing users to segment their networks into smaller, isolated broadcast domains. pfSense has native support for VLAN routing, while OPNsense’s VLAN features can be used to divide networks into smaller, more manageable groups. pfSense is a viable option if VLAN routing features are a top priority. Otherwise, OPNsense offers effective VLAN segmentation for various network requirements.

Your needs and preferences should guide your decision between OPNsense and pfSense. Each platform offers unique strengths, so consider your network’s needs, complexity, and familiarity with firewall management before making a decision.

What are the security features of pfSense and OPNSense?
Ajay Rathore is a tech-savvy individual with a passion for all things related to technology. He has a deep understanding of various hardware and software systems, and is always on the lookout for new advancements in the field. As a true geek, Ajay spends much of his free time tinkering with the latest gadgets and exploring new technologies. He is highly knowledgeable and skilled in programming languages, and has a keen eye for detail. Whether working on a project or helping others solve technical issues, Ajay is a valuable asset to any team.

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