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When we last saw Cerberus, the small form factor, low power, high performance IDS firewall, it was chewing through anything the net threw at it. Today’s question is: can Cerberus go for the gold and become a full-fledged Unified Threat Management (UTM) Appliance, capable of providing all of the protection required by a home network, let alone an enterprise network?

Cerberus, as the previous article detailed, is an IDS Firewall built around a mini-ITX 1.8 GHz dual-core Atom and 3 GB of memory, providing three heads of network protection: pfSense, a free open source project, providing standard perimeter firewall protection as part of an overall router, and two pfSense packages: Snort, the premiere open source Intrusion Detection and Prevention rules engine, and IP Blocklist, which uses dynamic categorical lists to block questionable traffic.

To build a capable UTM appliance, we first need to define what Unified Threat Management is. Once we understand that, we’ll step through adding and configuring those services to Cerberus, and finally look whether Cerberus can carry the weight or fall short in either functionality or performance.

What is a UTM Appliance?

The concept of Unified Threat Management is straightforward: on the outer reaches of your network perimeter, you install an appliance that stops all possible threats to your network, an über firewall, as it were. The fact of the matter is that UTM hardware is expected to completely overtake separate network protection hardware.

The problem is there is no single definition of the services required in a UTM appliance. For example, one of the foremost makers of UTM appliances for the enterprise, Endian, lists an entire dense page of functionality. In comparison, Untangle, a small organization UTM, lists only about twenty functions.

So what do they have in common? For our purposes, a UTM appliance is something that offers Intrusion Protection Firewall, Anti-Virus, Anti-Spam, and Traffic Control features. Beyond this core protection, a UTM appliance generally includes some enterprise operation capabilities, such as load balancing, fail-over, and network wide caching and monitoring.

UTM diagram

pfSense can perform all these functions to some extent. To judge how well pfSense meets these UTM requirements, I’ve given a subjective grade to each set of UTM function groups. Once we’ve defined how these functions thwart threats, and how pfSense meets those challenges, we’ll upgrade Cerberus, and see how it performs as a UTM.

Intrusion Detection and Prevention (IDS/IPS)

Snort logoAs detailed in the first article, IDS uses a packet inspection engine in conjunction with a standard NAT firewall to recognize patterns in network traffic, either at the packet level or at the stream level. IDS uses dynamic rules to spot these irregularities, such as protocol vulnerabilities, port scans, Denial of service attacks, and alike.

The vast majority of UTM appliances utilize Snort, the most widely deployed IDS/IPS rules engine. Snort uses rules that are updated regularly from pfSense has wrapped Snort in an easy to install and administer WebGUI package.

Cerberus is already configured for Snort, so we’ll not be covering that as part of the upgrade process. For detailed instructions on how to install and configure Snort, please refer to the previous article.

pfSense Grade: A


The ability to block the Internet’s malicious flora and fauna from infecting network clients is core to any UTM. This is accomplished by inspecting packets for establish virus signatures and virus meta-patterns.

HAVP logopfSense includes the HAVP package:  HTTP Anti-Virus Proxy, a transparent proxy that scans all HTTP traffic for malware signatures. HAVP utilizes ClamAV, the open source and community anti-virus engine for Linux and BSD distros.

Naturally, the question of effectiveness is raised when using an open source anti-virus solution versus a commercial product. But is difficult to make a clear determination of effectiveness. Some reports place ClamAV in the top five, others in the bottom five.

There is a dirty little secret in anti-virus detection. Most anti-virus programs are good at detecting known malware. But with the preponderance of free Anti-virus solutions, virus writers are able to craft their code to avoid most prevention solutions, they can test their code before it is released into the wild.

This means that anti-malware solutions effectiveness should really be measured in latency, from the point that they are first seen in play, to when they are added to their respective detection databases. Commercial vendors run network scanners, honeypots, and have dedicated personnel associated with finding the newest threats. ClamAV does not have such resources and hence operates at a disadvantage.

HAVP, as the name implies, is also limited to HTTP traffic. This means that viruses imbedded in files transferred via FTP, HTTPS, and other protocols such as P2P are not examined and would not be detected. Neither are e-mail attachments scanned, which account for one of the largest causes of malware infections.

Because of this, it is important that UTM based anti-virus not be your only malware line of defense. Per client, anti-virus is a critical part of any network’s protection. With so many quality products that can be had at little or no cost, there is no excuse not to run anti-virus on each network host.

Additionally, since it is strongly recommended that you run only one anti-virus application per host, HAVP does have significant utility, because HTTP is one of the largest vectors for infection. HAVP gives you two bites at the apple and offers protection against malware that is targeted at closed systems, such as cell phones and Internet-enabled home theater components.

pfSense Grade: C-

Content Filtering

Content filtering is what it sounds like: the ability to block certain and generally NSFW content from your network. Such content is typically porn, gambling, file sharing, and hacking methods, but can extend to bandwidth-consuming audio/video sites and time-consuming social networking, forum, and blog sites.

Most importantly, it can be used to block IP addresses associated with spamming, malware, and addresses deemed to be compromised in some other way. Unless you have kids, this is the category that is of the most interest to home networks.

pfSense excels at content blocking and offers four different packages for controlling what can come in your front door.

Content Blocking Packages
DNS Blacklist Included functionality uses a static category list Domain blocking by category
Country Block Add-on Package Block entire country access
Squid Guard Add-on Package, works in conjunction with Squid Caching Proxy Server Full Featured URL filter
IP Blocklist Add-on Package, uses frequently updated categorical address lists from Block IP Addresses based on diverse set of lists

Both Country Block and DNS Blacklist are simple. DNS Blacklist, which use a simple list of categories, is a real grab bag and allows the standard blocking of adult and gambling sites, but also astrology, and for some reason, French educational institutes sites (?!?).

IP Blocklist, which had its origins in the P2P peer blocking arena, blocks hosts that perform IP tracking for media companies and associations like the RIAA and the MPAA. It has grown to allow the blocking of spammers, advertising, malware, and other compromised sites. The lists differ significantly in quality; some are excellent, with spot-on targeting, while others seem ill-maintained, and hence have unintentional causalities - for example, one of the adware lists blocks all of CNet.

Squid Guard logoThe real star here is Squid Guard, which works with the caching proxy server Squid. Squid Guard allows for Access Control Lists for specific IPs, with scheduling and user-defined redirect pages. It comes with a built-in blacklist, but also allows the use of community-maintained categorical blacklists. Squid Guard is an ideal solution for café hotspots, schools and libraries.

pfSense Grade:  B

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