HackerOne - HackerOne provides a platform designed to streamline vulnerability coordination and bug bounty program by enlisting hackers.
WhoisThisDomain - Domain name lookup tool that allows you to get information about domain registration from WHOIS server.
Acunetix - Audit your website security and web applications for SQL injection, Cross site scripting and other...
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.
Forcepoint Web Security Suite - Internet Security
Whoisology - Connected database of whois records and whois history