What things do we need before performing a great enumeration?
1) API keys for Passive DNS data
What is Passive DNS data?
Problems with obtaining free API keys of good passive sources:
Is it worth making API keys?
How much time does it takes to signup and obtain API keys?
2) 100% accurate open public DNS resolvers
Why do we need a public DNS resolvers list?
How can we create a list of public resolvers?
3) A VPS (Most Preferable)