Penetration Testing

What is Penetration Testing?

Penetration Testing (short: pentest) is an authorized, simulated cyberattack on your IT infrastructure, web applications, or networks. The goal is to identify security vulnerabilities before real attackers exploit them.

Unlike automated vulnerability scans that detect known weaknesses, a pentest goes much further:

• Manual Analysis: Experienced testers combine tools with human know-how
• Exploitation: Discovered vulnerabilities are actively exploited to demonstrate potential damage
• Chain Attacks: Multiple smaller weaknesses are combined to gain deeper access
• Business Impact: Not only technical gaps, but also their impact on business processes are evaluated

Studies show: Companies with regular pentest programs detect security breaches an average of 92 days faster than those without structured testing.

The Three Pentest Types: Black Box, White Box, Gray Box

Penetration tests are categorized by the tester's level of knowledge. Each approach has specific advantages and disadvantages.

Black Box Testing: The External Attacker

In a Black Box Pentest, the tester receives no prior information about the target environment. They start like a real external attacker: with zero knowledge.

Typical Process:

1. Reconnaissance: Gathering publicly available information (WHOIS, DNS, Social Media, employee profiles)
2. Scanning & Enumeration: Identifying open ports, running services, technology stack
3. Exploitation: Exploiting discovered vulnerabilities
4. Post-Exploitation: Lateral Movement, Privilege Escalation, establishing persistence

Advantages:

• Most realistic simulation of a real attack
• Tests what an outsider without insider knowledge can achieve
• Tests outer defense lines (firewall, perimeter security)

Disadvantages:

• Time-intensive - reconnaissance phase can take weeks
• Higher costs due to longer test duration
• Risk of overlooking internal vulnerabilities (if tester doesn't get into the network)
• False Security: Defensive tools can block attacks and obscure vulnerabilities

Ideal for: Organizations that want to test their external attack surface and incident response capabilities.

White Box Testing: The Transparent View

In a White Box Pentest, the tester receives complete access to all relevant information:

• Network diagrams and architecture documentation
• Application source code
• Administrator access and credentials
• Configuration files from servers and network devices

Focus:

• Logical vulnerabilities in applications
• Security misconfigurations
• Faulty code (Code Review + dynamic testing)
• Insufficient defense mechanisms

Advantages:

• Most comprehensive analysis - no blind spots
• Faster than Black Box (no time-consuming reconnaissance)
• Also reveals vulnerabilities that are not visible from outside
• Enables static code analysis (Static Application Security Testing, SAST)

Disadvantages:

• Unrealistic for external attackers (they don't have source code access)
• Doesn't test detection capabilities (since no "real" attacks are performed)

Ideal for: Critical systems (payment processing, health data), compliance validation (PCI-DSS, HIPAA), pre-release tests of new applications.

Gray Box Testing: The Insider Threat

The Gray Box Pentest lies between Black and White Box. The tester receives limited information - such as:

• Low-privileged user accounts
• Network diagrams (but no admin access)
• Documentation of main components (but no source code)

This approach simulates an insider attack or an attacker who has already breached the outer defense line (e.g., via phishing).

Advantages:

• More efficient than Black Box (less time for reconnaissance)
• Can focus on the riskiest systems
• Reveals lateral movement paths and privilege escalation
• Realistic scenario for insider threats

Disadvantages:

• Not a complete simulation of external attacks
• Requires clear definition of what info the tester receives

Ideal for: Companies with complex hybrid cloud environments, organizations wanting to minimize insider risks, testing post-breach scenarios.

Pentest Methodology: How Does a Professional Pentest Work?

Serious penetration tests follow established methods such as PTES (Penetration Testing Execution Standard), OWASP Testing Guide, NIST SP 800-115, or MITRE ATT&CK Framework.

A typical process includes the following phases:

Phase 1: Scoping & Planning

Before the test begins, the framework is defined:

• Scope: Which systems, applications, networks will be tested?
• Rules of Engagement: What is allowed? (e.g., social engineering, DoS tests, physical access)
• Timeframe: When will the test take place? (business hours, nights, weekends)
• Contact persons: Who gets notified for critical findings?
• Legal: Contracts, liability waivers, NDA

Phase 2: Reconnaissance

The tester gathers information about the target. We distinguish:

• Passive Reconnaissance: Information gathering without direct interaction (OSINT, Google Dorking, Social Media, WHOIS, DNS)
• Active Reconnaissance: Direct interaction (port scans, service enumeration, fingerprinting)

Typical tools: nmap, Shodan, theHarvester, Recon-ng

Phase 3: Vulnerability Assessment

Identified systems are scanned for vulnerabilities:

• Known CVEs (Common Vulnerabilities and Exposures)
• Misconfigurations (open ports, default credentials)
• Outdated software versions
• Web vulnerabilities (SQL Injection, XSS, CSRF)

Important: 95% of a professional pentest consists of manual work. Automated scanners only provide the foundation.

Typical tools: Nessus, OpenVAS, Burp Suite, Metasploit

Phase 4: Exploitation

Now it gets serious: Discovered vulnerabilities are actively exploited.

• Initial Access: Gaining access to a system (e.g., via Remote Code Execution)
• Privilege Escalation: Moving from user to admin rights
• Lateral Movement: Compromising additional systems in the network
• Data Exfiltration: Identifying and (within scope) extracting sensitive data
• Persistence: Establishing backdoors to secure access

Ethical Boundaries: The tester documents the attack path but only executes what was agreed upon in the scope. Data destruction or DoS attacks only occur after explicit approval.

Phase 5: Post-Exploitation

The goal is to evaluate the potential damage:

• How far can an attacker get?
• Which critical assets are reachable?
• Can data be exfiltrated?
• Would a complete system takeover be possible?

Phase 6: Reporting

The pentest report is the end product. A good report contains:

• Executive Summary: Management-friendly summary (without technical jargon)
• Methodology: How was testing performed? Which tools?
• Findings: All identified vulnerabilities, sorted by severity (Critical, High, Medium, Low)
• Proof of Concept: Screenshots, logs, exploit code - proof that the vulnerability is real
• Remediation Advice: Concrete recommendations for remediation
• Attack Chains: How did initial access lead to complete compromise?

Phase 7: Remediation & Re-Test

After the pentest, the real work begins:

1. Prioritize findings (by CVSS score and business impact)
2. Implement fixes
3. Perform re-test to verify vulnerabilities are remediated

Many providers include a free re-test after the remediation phase.

When Do You Need a Pentest?

Penetration testing makes sense not just for large corporations. The following triggers should initiate a pentest:

• New application before go-live: Pre-production pentest reveals vulnerabilities before users are affected
• After major updates: Architecture changes, new features → new attack surface
• Compliance requirements: PCI-DSS, ISO 27001, HIPAA, NIS2 require regular pentests
• M&A due diligence: Buyers want to know how secure the target company is
• After an incident: Post-breach assessment shows how the attack was possible
• Regularly (annually or more): The threat landscape changes - your security should keep pace

Pentest vs. Vulnerability Scan: What's the Difference?

Many confuse penetration testing with automated vulnerability scans. Here's the difference:

Criterion	Vulnerability Scan	Penetration Test
Automation	Fully automated	95% manual
Vulnerabilities	Identify	Identify & exploit
False Positives	Frequent	Rare (Proof of Concept)
Business Impact	Technical assessment	Business-oriented risk analysis
Frequency	Continuous / weekly	Annually / when changes occur
Cost	Low	Medium-High

Conclusion: Both complement each other. Scans provide continuous monitoring, pentests provide deep analysis and exploitation.

Common Mistakes in Penetration Tests

1. Too Narrow Scope

Some organizations limit scope too much ("Only these three servers"). This causes potential attack paths to be missed. An attacker doesn't adhere to your scope definitions.

2. No Follow-Up

The report ends up in a drawer, findings aren't remediated. A pentest without remediation is wasted money.

3. Only Once Every Five Years

The threat landscape evolves faster. Annual tests (or more frequent) are state of the art.

4. Wrong Expectations

A pentest is not a free pass ("We were tested, so we're secure"). It's a snapshot. New vulnerabilities emerge daily.

5. Cheap Providers Without Expertise

A poor pentest is worse than no pentest - it creates a false sense of security. Look for certifications (OSCP, CEH, GPEN) and references.

Pentest Certifications: What Do They Mean?

Reputable pentesters hold recognized certifications:

• OSCP (Offensive Security Certified Professional): Gold standard for practical penetration testing
• CEH (Certified Ethical Hacker): Widely recognized, focused on tools and methods
• GPEN (GIAC Penetration Tester): Deep technical expertise
• CREST: International accreditation for pentest companies

Ask for certificates - and for practical experience. A good pentester has both.

Red Team vs. Pentest: What's the Difference?

A Red Team Engagement goes beyond traditional penetration testing:

• Objective: Not just finding vulnerabilities, but achieving specific business goals (e.g., "gain access to customer data")
• Duration: Weeks to months (vs. days for pentests)
• Scope: Everything is allowed - phishing, social engineering, physical access
• Stealth: Red teams operate undetected to also test detection capabilities

Red teaming tests the entire security organization - technical, process, and personnel. It's the stress test for mature security programs.

Conclusion: Test or Be Tested

Cybersecurity is not a static state. Your environment changes, threats evolve, new vulnerabilities emerge. A penetration test shows you where you stand - here and now.

The question is not whether you will be tested. The question is: By whom? By an authorized pentester who helps you fix vulnerabilities? Or by a real attacker who doesn't care about your customer data, reputation, and business model?

The answer is obvious. Invest in regular penetration tests. Take findings seriously. Fix vulnerabilities systematically. And repeat the process.

Because one thing is certain: Attackers don't sleep. Your security shouldn't sleep either.