Service Fingerprinting

Overview

Service fingerprinting identifies the specific software, version, and configuration of network services. Accurate fingerprinting enables targeted vulnerability assessment, exploit selection, and understanding of the attack surface. This skill combines active probing, banner grabbing, and behavioral analysis.

Core principle: Start passive, escalate to active when needed. Combine multiple techniques for accuracy.

When to Use

• After discovering live hosts (from subdomain enumeration)
• Before vulnerability scanning or exploitation
• When building detailed target intelligence
• During penetration testing reconnaissance phase

Techniques

Port Scanning

# Fast SYN scan of common ports
nmap -sS -F target.com

# Comprehensive scan of all ports
nmap -p- -T4 target.com

# Service version detection
nmap -sV -p 80,443,22,3306 target.com

# OS detection
sudo nmap -O target.com

# Aggressive scan (version, OS, scripts, traceroute)
nmap -A target.com

Banner Grabbing

# Manual banner grab
nc target.com 80
GET / HTTP/1.0

# Automated with nmap
nmap -sV --version-intensity 9 -p 80,443 target.com

# Multiple services
for port in 21 22 25 80 443 3306; do
  echo "=== Port $port ===" 
  nc -w 2 target.com $port
done

HTTP/HTTPS Fingerprinting

# Detailed HTTP headers
curl -I https://target.com

# Technology detection
whatweb -a 3 https://target.com

# Certificate information
echo | openssl s_client -connect target.com:443 2>/dev/null | openssl x509 -noout -text

Specialized Scanners

# Database fingerprinting
nmap -p 3306 --script mysql-info target.com
nmap -p 5432 --script pgsql-info target.com

# SMB enumeration
nmap -p 445 --script smb-os-discovery target.com

# SSH fingerprinting
ssh-audit target.com

Common Services

Integration with Other Skills

• skills/reconnaissance/automated-subdomain-enum - Provides targets
• skills/reconnaissance/web-app-recon - Detailed HTTP analysis
• skills/exploitation/* - Informs exploit selection