Information gathering sites and tools
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hunter.io
VoilàNorbert
phonebook.cz
EmailHippo
DeHashed
DeHashed: non free service but can be paid for a week, a month, a year
Can use: mail, ip, username, addres, phone
Also might return hash password: then go to hashes.org
sublist3r: Tool designed to enumerate subdomains of websites using OSINT.Can required your VirusTotal API key for maximum results
crt.sh
Holehe : checking performed on more than 120 sites among the most known and used