Shodan

Shodan continuously scans the internet and indexes what it finds: open ports, service banners, device types, vulnerabilities, screenshots of exposed interfaces. You search it like a search engine ("webcams in Los Angeles," "hosts running this software version") and monitor your own IP ranges for exposure. There's an API and a command line tool.

For T&S it's useful in investigations (what's hosted on a scam domain's IP, what else that server runs) and for tracking infrastructure abuse.