As we have explored so far, OPNsense is a stateful firewall with some extra features, such as an Intrusion Detection System (IDS) and an Intrusion Prevention System (IPS), that can extend its filtering capabilities. But to compete head-to-head with the well-known commercial firewall solutions from giant cybersecurity tech firms, an open source firewall must have all the capabilities those solutions offer. There was a chasm between commercial and open source network firewalls due to the layer7 filtering feature being present only in the commercial ones. The ability to detect traffic, despite the TCP/IP port number, is a must-have feature these days, especially when malware tries to bypass stateful inspection by mimicking legitimate traffic.

The OPNsense project implemented some application control features, thus creating custom signatures for IPS, which we tested in the previous chapter. Still, its application control wasn’t at the...