Knowing what services are running on your systems, and being able to identify if and when any of those services change, is the first step in securing your netwsork. Many tools can accomplish this, but ...

Network recon framework. Build your own, self-hosted and fully-controlled alternatives to Shodan / ZoomEye / Censys and GreyNoise, run your Passive DNS service, build your taylor-made EASM tool, ...