Suricata is an Intrusion Detection and Prevention (IDS/IPS) engine developed by the Open Information Security Foundation and its supporting vendors. The engine is multi-threaded and has native IPv6 support, file extraction capabilities, and many more features. It's capable of loading existing Snort rules and signatures, and supports many frontends through Barnyard2.
Nova is a software application for preventing and detecting hostile network reconnaissance (such as nmap scans). It does this by first creating the Haystack: a large collection of low interaction honeypots using an updated version of Honeyd. Finding real machines on the network becomes like finding a needle in a haystack of fake machines. Second, Nova uses machine learning algorithms to automatically detect and classify attempts at hostile reconnaissance, so there's no need to go searching manually through your honeypot's log files. It provides an easy to use Web-based interface powered by Node.js to configure itself and Honeyd instances.