Footprinting and Recon:

	https://hackernoon.com/https-medium-com-aamralkar-footprinting-and-reconnaissance-e14010b22a89

	https://www.tutorialspoint.com/ethical_hacking/ethical_hacking_footprinting.htm

	https://en.wikipedia.org/wiki/Footprinting

OSINT:

	https://medium.com/bugbountywriteup/a-guide-to-open-source-intelligence-gathering-osint-ca831e13f29c

	https://en.wikipedia.org/wiki/Open-source_intelligence

	https://osintframework.com/

	https://www.greycampus.com/blog/information-security/top-open-source-intelligence-tools

	https://www.peerlyst.com/posts/top-20-open-source-intelligence-osint-tools-you-should-know-in-2020-chiheb-chebbi

Email Footprinting

	http://www.emailtrackerpro.com/

	https://it.umn.edu/gmail-view-email-headers

Website Footprinting:

	https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers

	https://www.tutorialspoint.com/http/http_header_fields.htm

	https://en.wikipedia.org/wiki/List_of_HTTP_header_fields

Footprinting Using Google:

	https://gist.github.com/stevenswafford/393c6ec7b5375d5e8cdc

	https://gbhackers.com/latest-google-dorks-list/

	https://github.com/BullsEye0/google_dork_list

Competitive Intelligence:

	https://www.shopify.in/encyclopedia/competitive-intelligence

	https://en.wikipedia.org/wiki/Competitive_intelligence

DNS Footprinting:

	https://www.iana.org/about

	https://en.wikipedia.org/wiki/Internet_Assigned_Numbers_Authority

	https://en.wikipedia.org/wiki/ICANN

	https://en.wikipedia.org/wiki/Regional_Internet_registry

	https://www.whois.net/

	http://whois.domaintools.com/

	https://who.is/

	https://www.whois.com/

	https://www.cisco.com/c/en/us/support/docs/ip/domain-name-system-dns/12684-dns-resource.html

	https://en.wikipedia.org/wiki/List_of_DNS_record_types

	http://www.dnsstuff.com

	http://network-tools.com

	https://domainpunch.com/dnapro/

	http://www.webextractor.com/

	https://github.com/lanmaster53/recon-ng

Network Footprinting:

	https://help.fasthosts.co.uk/app/answers/detail/a_id/1550/~/traceroute-explained

	https://www.inmotionhosting.com/support/website/ssh/read-traceroute/

	https://www.geeksforgeeks.org/traceroute-in-network-layer/

	https://www.geeksforgeeks.org/difference-between-ping-and-traceroute/

Countemeasures:

	http://luizfirmino.blogspot.com/2011/09/footprinting-countermeasures.html

	https://www.w3schools.in/ethical-hacking/footprinting/#Countermeasures

	https://www.techopedia.com/definition/1346/split-domain-name-system-split-dns

	https://www.webopedia.com/TERM/S/split_DNS.html