Open Source Intelligence Techniques — Michael Bazzell
inteltechniques.com
Official site with book updates, podcast & tools (current edition available on Amazon)
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Bellingcat Resources
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Bellingcat Online Investigation Toolkit
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Live, searchable toolkit maintained by Bellingcat
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SANS Reading Room — OSINT
sans.org
Peer-reviewed whitepapers (free with registration)
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SANS Reading Room — Forensics
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DFIR whitepapers, free
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SANS SEC497 OSINT Course
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