Deepinfo - Know your attack surface. Empower your security.
WhoisThisDomain - Domain name lookup tool that allows you to get information about domain registration from WHOIS server.
SecurityScorecard - Security solution to predict and remediate potential security risks across organizations and their partners.
Whoisology - Connected database of whois records and whois history
UpGuard - Visibility into the state of your IT infrastructure, enabling you to understand your risk potential, prevent breaches, and speed up software delivery.
Bulk Whois API - Bulk Whois API is a provider of parsed WHOIS data in JSON with simple API, competitive pricing, top notch support, and more.