Create lab1-osint-basics.md

Author: ngvuthdanhh

labs/lab1-osint-basics.md

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+# Lab 1 – OSINT Basics for DFIR
+
+## Objective
+Learn how to collect publicly available information relevant to an incident.
+
+## Tasks
+1. Perform domain lookups (WHOIS, DNS, certificates).
+2. Identify related infrastructure (subdomains, IP allocations).
+3. Check reputation platforms (VirusTotal, AbuseIPDB).
+4. Collect indicators and document findings.
+
+## Expected Output
+- IOC list  
+- Screenshots of queries  
+- Summary of correlations