Censys continually monitors every reachable server and device on the Internet. Complete wealth of knowledge of internet connected devices.
Check-Host is a modern online tool for website monitoring and checking availability of hosts, DNS records, IP addresses. It supports the latest technologies such as localized domain names (both punycode and original formats), hostname IPv6 records (also known as AAAA record).
We have developed a Linux based script (require a Ubuntu installation) using this service to batch lookup a list of IP's. Read more about the script here.
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Check if malicious or cyrillic domains are registered. Free, simple and easy to use.
Collection of historical DNS information. Free, simple and easy to use.
The World's Largest Repository of historical DNS data. Free, simple and easy to use.
Domainhistory is a free service that gives you previous whois info
Check your own IP, handy to check if your VPN is working.
Simple & fast programmatic IP address lookup for your website & mobile app
Best tool for checking up domains, ip numbers, mail headers, MX, TXT records etc etc.
An alternative to MX Toolbox.
Check what's linking to a specific URL.
Collects, stores and analyses data from thousands of passive DNS collection sensors. Complete unadulterated historical and current DNS information.
Cons: 15 API calls day, 15 web based searches a day.
Robtex is used for various kinds of research of IP numbers, Domain names, etc
IRC search tool
Internet of things search engine. Can find heaps of misconfigured network connected devices.
Takes the information from public sources, then structure it for your quick and convenient search for the websites that probably belong to the same owner. Great for retrieve websites and their Tracking codes.
Shows geo data about IP´s.
An alternative to MX Toolbox.
Find out what email addresses are connected to a domain