Everscan is a daemonized network scanner that randomly scans at a very slow pace for machines and stores the data to a database. It comes with a client to query for finds.
You can download it from the following link: https://packetstormsecurity.com/files/download/34920/everscan-0.8.2.tgz
Source: https://packetstormsecurity.com/files/34920/everscan-0.8.2.tgz.html