Reconnaissance & Information Gathering

Reconnaissance (recon) is the first active phase of a penetration test. It involves collecting as much information as possible about the target — before touching the target's systems directly. Good recon shapes your entire attack strategy and can reveal vulnerabilities without triggering any alarms.

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Reminder: All techniques in this lesson must only be performed against targets you have written authorisation to test.

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Passive vs Active Reconnaissance

Type	Definition	Detection Risk	Examples
Passive	Gathering info without interacting with the target	None	OSINT, Google dorking, WHOIS
Active	Directly probing the target's systems	Medium–High	DNS queries, port scans, pings

graph TD
  P["Passive Recon"] --> P1["Public records"]
  P --> P2["Social media"]
  P --> P3["Job postings"]
  P --> P4["Google dorking"]
  P --> P5["Shodan search"]
  P1 --> PN["No direct contact with target systems"]
  A["Active Recon"] --> A1["DNS enumeration"]
  A --> A2["Port scanning"]
  A --> A3["Banner grabbing"]
  A --> A4["Web spidering"]
  A --> A5["SNMP queries"]
  A1 --> AN["Direct interaction with target systems"]

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OSINT (Open Source Intelligence)

OSINT uses publicly available information. Key sources include:

Domain and IP Information

# WHOIS lookup — domain registration details
whois example.com

# DNS lookups
dig example.com ANY
dig example.com MX
dig example.com TXT

# Reverse DNS
dig -x 93.184.216.34

# Find the ASN (Autonomous System Number)
whois -h whois.radb.net -- '-i origin AS15169'

DNS Enumeration & Subdomain Discovery

Subdomains often expose development, staging, or internal services:

# Using subfinder (passive subdomain enumeration)
subfinder -d example.com -o subdomains.txt

# Using amass (comprehensive enumeration)
amass enum -passive -d example.com

# Using dnsrecon
dnsrecon -d example.com -t std

# DNS zone transfer attempt (active — only with authorisation)
dig @ns1.example.com example.com AXFR

Useful OSINT Tools

Tool	Purpose	URL
Shodan	Search engine for internet-connected devices	shodan.io
Censys	Internet-wide scanning data	censys.io
theHarvester	Email, subdomain, IP gathering	Built into Kali
Maltego	Visual link analysis and OSINT	maltego.com
Recon-ng	Modular OSINT framework	Built into Kali
SpiderFoot	Automated OSINT collection	spiderfoot.net

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Google Dorking

Google advanced search operators can reveal sensitive information accidentally exposed on the web:

# Find login pages
site:example.com inurl:login

# Find exposed configuration files
site:example.com filetype:env OR filetype:cfg OR filetype:conf

# Find directory listings
site:example.com intitle:"Index of /"

# Find exposed documents
site:example.com filetype:pdf OR filetype:xlsx OR filetype:docx

# Find subdomains indexed by Google
site:*.example.com -www