Inline Intrusion Prevention System

The inline IPS system of OPNsense is based on Suricata and utilizes Netmap to enhance performance and minimize cpu utilization. This deep packet inspection system is very powerful and can be used to mitigate security threats at wire speed.

Emerging Threats ETOpen Ruleset

The ETOpen Ruleset is an excellent anti-malware IDS/IPS ruleset that enables users with cost constraints to significantly enhance their existing network-based malware detection. The ETOpen Ruleset is not a full coverage ruleset, and may not be sufficient for many regulated environments and should not be used as a standalone ruleset.

OPNsense has integrated support for ET Open rules. For details and Guidelines see: For rules documentation: offer several blacklist for protecting against fraudulent networks. OPNsense has integrated support for:

SSL Blacklist

SSL Blacklist (SSLBL) is a project maintained by The goal is to provide a list of “bad” SSL certificates identified by to be associated with malware or botnet activities. SSLBL relies on SHA1 fingerprints of malicious SSL certificates and offers various blacklists.

See for details:

Feodo Tracker

Feodo (also known as Cridex or Bugat) is a Trojan used to commit ebanking fraud and steal sensitive information from the victims computer, such as credit card details or credentials. At the moment, Feodo Tracker is tracking four versions of Feodo, and they are labeled by Feodo Tracker as version A, version B, version C and version D:

  • Version A Hosted on compromised webservers running an nginx proxy on port 8080 TCP forwarding all botnet traffic to a tier 2 proxy node. Botnet traffic usually directly hits these hosts on port 8080 TCP without using a domain name.
  • Version B Hosted on servers rented and operated by cybercriminals for the exclusive purpose of hosting a Feodo botnet controller. Usually taking advantage of a domain name within ccTLD .ru. Botnet traffic usually hits these domain names using port 80 TCP.
  • Version C Successor of Feodo, completely different code. Hosted on the same botnet infrastructure as Version A (compromised webservers, nginx on port 8080 TCP or port 7779 TCP, no domain names) but using a different URL structure. This Version is also known as Geodo and Emotet.
  • Version D Successor of Cridex. This version is also known as Dridex

See for details:

URLHaus List

With OPNsense version 18.1.7 we inroduced the URLHaus List from which collects compromised sites distributing malware.

See for details:

Finger Printing

OPNsense includes a very polished solution to block protected sites based on their SSL fingerprint.

App detection rules

With OPNsense version 18.1.11 we introduced the app detection ruleset. Since about 80 percent of traffic are web applications these rules are focused on blocking web services and the URLs behind them.

If you want to contribute to the ruleset see: