Understanding how attackers think is the best way to build secure systems. Here's the pentester mindset — for defenders.
A penetration test (pentest) is an authorized simulated attack on a system to find vulnerabilities before real attackers do. The methodology:
1. Reconnaissance — gather information
2. Scanning — identify open ports, services
3. Exploitation — attempt to compromise
4. Post-exploitation — what can be done with access
5. Reporting — document findings with severity ratings
Before touching a target, pentesters gather public information:
# DNS enumeration
nslookup target.com
dig target.com ANY
# Subdomain discovery
subfinder -d target.com
amass enum -d target.com
# Certificate transparency logs (reveals subdomains)
# Check: crt.sh
# WHOIS
whois target.com
# Technology detection
whatweb target.com# Port scanning with nmap
nmap -sV -sC -p- target.com
# Web application scanning
nikto -h target.com
# Directory brute-forcing
gobuster dir -u https://target.com -w /wordlists/common.txtOWASP Top 10:
1. Broken Access Control
2. Cryptographic Failures
3. Injection (SQL, XSS, etc.)
4. Insecure Design
5. Security Misconfiguration
6. Vulnerable Components
7. Authentication Failures
8. Data Integrity Failures
9. Security Logging Failures
10. SSRF
You don't need to be a pentester. But understanding what they look for changes how you build:
The best security is built by developers who think like attackers.
Practice on intentionally vulnerable apps:
Never test systems you don't have permission to test.