What Is Penetration Testing in Software Testing? Types, Steps & Examples

If you build or test software today, you’re shipping into a world where the average cost of a data breach is around USD 4.88 million. At the same time, most breaches now involve web apps, APIs, cloud services, or human error, not just traditional network attacks.

That’s why “What is penetration testing in software testing?” is no longer a niche question. It’s a core skill for anyone who cares about software quality and user trust.

This guide will walk you through:

• What penetration testing actually is (in plain English)
• How it fits into software testing and SDLC
• Types of penetration testing used in modern projects
• The 5 key steps of a penetration test
• Examples from real-world software scenarios
• How pen testing differs from vulnerability scanning
• Best practices, limitations, and FAQs

Penetration testing in software testing is a type of non-functional security testing where ethical hackers simulate real cyberattacks against your applications, APIs, and infrastructure to identify and exploit vulnerabilities under controlled conditions, then report exactly how to fix them before attackers can.

1. What is penetration testing in software testing?

Most reputable sources define penetration testing as an authorized, simulated cyberattack on a system to uncover and verify security weaknesses.

In the context of software testing, penetration testing:

• Focuses on applications, APIs, and the platforms they run on
• Uses the same tools and techniques as attackers (SQL injection, XSS, privilege escalation, etc.)
• Goes beyond “finding” bugs, testers actively exploit them (safely) to prove impact
  

Put simply:

Penetration testing = ethical hacking as part of your QA and security process.

It’s different from unit, integration, or UI testing. Those verify expected behavior. Pen testing focuses on what shouldn’t be possible, like bypassing authentication, stealing data, or taking over accounts.

Where does it sit in the testing taxonomy?

From a software-engineering point of view, penetration testing is:

• Non-functional testing (it tests security and robustness, not business features)
• A specialized form of security testing, alongside code review, SAST, DAST, and threat modeling
• Usually performed after functional testing is stable, but increasingly integrated into CI/CD and DevSecOps workflows

2. Why penetration testing matters for modern software

A quick look at recent data explains why pen testing has become essential:

• IBM’s Cost of a Data Breach Report 2024 places the global average breach cost at USD 4.88 million, a 10% increase year-over-year.
• The UK Cyber Security Breaches Survey 2024 found that the most disruptive cyber incident cost medium and large businesses around £10,830 on average, and that’s just direct cost, not long-term brand damage.
• Verizon’s 2024 DBIR shows that 68% of breaches involve a human element (phishing, misconfigurations, or errors) and that system intrusion plus web application attacks dominate across many industries.
• A 2024 study on mobile app security found 62% of organizations had at least one mobile app breach in the previous year, despite 93% being confident in their security.

Based on current trends, the problem isn’t just attackers getting “smarter”, it’s software moving faster than traditional security checks can keep up.

In my experience, teams that only rely on scanners or periodic audits tend to:

• Miss complex, chained vulnerabilities
• Underestimate how much damage an attacker can do with “just one bug”
• Struggle to convince leadership to invest in security, because they lack clear, business-focused evidence

Penetration testing solves that by turning vague risk into concrete proof:

• “This API bug allowed us to exfiltrate 10,000 customer records in 3 minutes.”
• “This misconfigured S3 bucket gave us write access to production logs.”
• “With this IDOR issue, we escalated from ‘basic user’ to ‘super admin’ in two requests.”
  

That’s the kind of insight that changes budget conversations quickly.

3. How penetration testing fits into the software testing lifecycle

Penetration testing isn’t a one-off checkbox, it’s a repeatable activity in your SDLC.

A simple way to visualize it:

1. Design & requirements
   Threat modeling and security requirements start here.
   
2. Development
   
   • Static Application Security Testing (SAST)
   • Secure coding practices and code reviews
     
3. Testing & integration
   
   • Unit, integration, system, and regression tests
   • Dynamic Application Security Testing (DAST) in staging
   • Targeted penetration testing on high-risk features (auth, payments, data export)
     
4. Pre-release / go-live
   
   • Full-scope penetration test of the app, APIs, and infrastructure
   • Fixing and retesting critical findings
     
5. Post-release & maintenance
   
   • Regular pen tests (e.g., annually or after major changes)
   • Continuous scanning and monitoring
   • Retesting previous findings to prevent regressions

Pro tip (for QA and Dev teams): Treat pen test findings as first-class backlog items with severity, owner, and due dates, not as “security homework” that sits in a PDF.

4. Types of penetration testing in software testing

There are several ways to categorize penetration tests. In software projects, the most useful lenses are knowledge level, scope, and perspective.

By knowledge level (white, black, grey box)

• Black-box testing: Testers know almost nothing about the internal design. They behave like external attackers, discovering assets and weaknesses from scratch.
• White-box testing: Testers get full access: source code, architecture diagrams, credentials. This allows very deep, efficient testing and is often favored in secure SDLC programs.
• Grey-box testing: A middle ground: limited knowledge (e.g., user credentials, API docs), mimicking real-world attackers who’ve gained partial access.
  

By scope (what’s being tested)

Common scopes within software testing include:

• Web application penetration testing: Websites, portals, and SPAs
• API penetration testing: REST, GraphQL, gRPC, internal & external APIs
• Mobile app penetration testing: Android, iOS, plus their backend APIs
• Cloud / container penetration testing: Cloud configurations, Kubernetes, serverless functions
• Infrastructure testing: Networks, servers, firewalls (often overlaps with traditional IT security)
  

By perspective (where attacks originate)

• External testing: From the internet or untrusted networks
• Internal testing: From inside the corporate network or as an authenticated user
• Red teaming: Longer-term, stealthy simulations to test detection and response, not just vulnerabilities

In software testing, most teams start with web app + API pen testing, then extend to mobile and cloud as their environment grows.

5. What are the 5 steps of penetration testing?

Different frameworks (PTES, NIST SP 800-115, OWASP WSTG) describe the process slightly differently, but they agree on a phased, repeatable lifecycle.

A practical way to think about the five key steps:

1. Planning & scoping

• Define goals (e.g., “Can someone steal production customer data from this new portal?”)
• Agree on scope: domains, APIs, environments, out-of-bounds systems
• Clarify rules of engagement: test windows, data handling, how to report critical findings
• Make sure testers have proper legal authorization

2. Reconnaissance (information gathering)

• Mapping application endpoints, parameters, and flows
• Discovering APIs, subdomains, and third-party services
• Identifying frameworks, tech stacks, and known CVEs

In software testing, this phase often reveals “shadow APIs” and forgotten endpoints that never made it into official documentation.

3. Scanning & vulnerability analysis

• Using tools (like Burp Suite, ZAP, or custom scripts) to scan for:
  • Injection flaws
  • Broken authentication and session management
  • Misconfigurations
• Manually reviewing suspicious behaviors and error messages

Crucially, this is not just automated scanning, it’s guided by human understanding of business logic.

4. Exploitation & post-exploitation

This is where pen testing departs from normal QA:

• Testers attempt to exploit identified weaknesses:
  
  • Use SQL injection to read or modify database records
  • Abuse insecure direct object references (IDOR) to access other users’ data
  • Escalate from low-privilege account to admin
    
• Explore “what else is possible” once inside:
  
  • Pivoting between services
  • Lateral movement
  • Data exfiltration or privilege escalation
    

All of this happens under controlled conditions, with agreed safeguards for sensitive environments.

5. Reporting & remediation support

• Document each finding:
  
  • Description and technical details
  • Reproduction steps and evidence
  • Business impact in non-technical language
  • Severity and recommended fixes
    
• Walk through results with developers, QA, and leadership
• Support retesting after fixes

A good report doubles as a learning document that improves future design and coding practices.

6. Penetration testing vs vulnerability scanning

This is one of the most common People Also Ask questions, and one of the most misunderstood.

According to multiple security vendors and practitioners:

• Vulnerability scanning is:
  
  • Mostly automated
  • Breadth-first: finds known issues using signatures and rules
  • Great for routine checks and compliance
  • Limited in understanding business context and exploitability
    
• Penetration testing is:
  
  • Primarily manual, supported by tools
  • Depth-first: exploits vulnerabilities to assess real-world impact
  • Simulates actual attackers’ thinking, chaining multiple weaknesses
  • Produces richer, actionable, business-focused insights

You can think of it like this:

A vulnerability scan says, “You might have 200 issues here.”
A pen test says, “We used these 2 issues to steal your customer database and gain admin access, here’s the proof and how to fix it.”

Both are important, but they serve different purposes. A mature software security program uses scanners continuously and commission pen tests at key milestones or for high-risk systems.

Common mistake: Treating vulnerability scans as “good enough” pen testing. This often leaves business logic flaws, complex chains, and misconfigurations completely undetected.

7. Is penetration testing functional or non-functional testing?

From a software-testing perspective, penetration testing is primarily non-functional, because it evaluates qualities like:

• Confidentiality
• Integrity
• Availability
• Resilience against malicious behavior

However, pen testing frequently uncovers functional defects too:

• Flows that behave differently under unexpected input
• Race conditions
• Error handling that exposes stack traces or sensitive data

So the best answer is:

Penetration testing is a form of non-functional security testing that often reveals hidden functional bugs.

8. Penetration testing examples in software projects

Example 1: Web application login & account takeover

A SaaS product introduces social login and multi-factor authentication (MFA). A pen test:

• Attempts credential stuffing and MFA bypass
• Tests password reset flows for token leakage
• Looks for IDOR issues in user profile and billing pages

Outcome: testers demonstrate that a flawed password-reset implementation allows them to reset any user’s password with a predictable token. The team fixes the issue and adds server-side rate limiting.

Example 2: API penetration testing for a mobile app

A fintech mobile app exposes a public API with endpoints for transactions and user balances.

A pen test:

• Enumerates endpoints and parameters
• Fuzzes authorization tokens and user IDs
• Attempts to modify transaction amounts and destinations
  

Outcome: testers show that by modifying a single request parameter, an attacker can view other users’ account balances. Developers implement proper authorization checks (e.g., enforcing user IDs from tokens rather than request body).

Example 3: Cloud misconfiguration in CI/CD

A DevOps team moves to a cloud-native pipeline using containers and serverless functions.

A pen test:

• Assesses IAM policies, roles, and trust relationships
• Attempts to escalate from a compromised CI runner to production workloads
• Tests storage buckets and secrets management

Outcome: testers demonstrate that a misconfigured CI role can access production secrets, allowing full compromise of the live environment. Security updates IAM policies, isolates environments, and introduces just-in-time access.

9. When should you run penetration tests in software testing?

There’s no one-size-fits-all rule, but some practical guidelines:

• Before major releases: Especially for new products, major architectural changes, or high-risk features (payments, authentication, data export).
• Regularly (e.g., annually or semi-annually): For critical customer-facing apps, APIs, and mobile apps.
• After significant infrastructure changes: Cloud migrations, new identity providers, third-party integrations.
• For compliance: Standards like PCI DSS, ISO 27001, and many regional regulations expect regular security testing and remediation.
  

Based on current industry practice, high-maturity teams are moving from “annual pen test” to a mix of:

• Continuous scanning and monitoring
• Targeted pen tests for new features
• Full-scope tests annually or after major changes

10. Who performs penetration testing?

Pen tests can be performed by:

• Internal security teams or red teams
  Pros: deep context about your systems; continuous engagement.
  Cons: possible blind spots due to familiarity.
  
• External penetration testing providers
  Pros: independent view, broader experience across industries, useful for audits and compliance.
  Cons: require good scoping and onboarding time.
  

Many organizations use a hybrid model: internal teams handle ongoing testing; external specialists are brought in for complex systems or regulatory needs.

Key skills for penetration testers include:

• Strong knowledge of web technologies, protocols, and frameworks
• Familiarity with tools like Burp Suite, Nmap, Metasploit, and custom scripts
• Understanding of OWASP Top 10, OWASP WSTG, NIST SP 800-115, PTES, and OSSTMM frameworks
• The ability to think like both an attacker and a software engineer

11. Best practices for penetration testing in software testing

To get maximum value from pen testing, especially in a fast-moving software environment:

1. Define clear, risk-based scope
   Focus on systems that store sensitive data, handle payments, or provide critical business functions.
   
2. Integrate with DevSecOps
   
   • Feed findings into your ticketing system
   • Link vulnerabilities to affected components or microservices
   • Automate retesting where possible
     
3. Use recognized methodologies
   Align with standards like OWASP WSTG, NIST SP 800-115, and PTES for consistent, auditable processes.
   
4. Prioritize fixes by business impact
   Not all “critical” CVEs are equal. Focus first on vulnerabilities that:
   
   • Allow data exfiltration
   • Lead to privilege escalation
   • Bypass authentication or authorization
     
5. Close the loop with retesting
   A pen test isn’t done until critical and high findings are verified as fixed.
   
6. Turn lessons into prevention
   Use results for:
   
   • Developer training (real examples from your codebase hit much harder)
   • Secure coding guidelines and code-review checklists
   • Architectural changes that remove entire classes of bug
     

Pro tip (for engineering leaders): Use pen-test results in your board and executive updates. When leadership sees “this single bug could have cost us millions,” it becomes much easier to justify secure-by-design investments.

12. Limitations of penetration testing (and what it doesn’t do)

Penetration testing is powerful, but it’s not magic. Important limitations:

• It’s a point-in-time assessment. New vulnerabilities will appear as code and infrastructure change.
• It cannot guarantee zero vulnerabilities, only that no critical ones were found within the agreed scope and time.
• It depends heavily on scope quality. If you exclude critical systems or give unrealistic constraints, results will be limited.
• It doesn’t replace:
  
  • Secure design and coding
  • Strong identity and access management
  • User awareness and operational security
    

Think of pen testing as one pillar in a broader security and quality strategy, not the entire house.

Frequently Asked Questions

1. What is penetration testing in software testing, with examples?

Penetration testing in software testing is when security specialists simulate attacks against your application to find exploitable weaknesses.

Example: A tester attacks the login and account pages of your web app, discovers an IDOR vulnerability, and proves they can view or change another user’s profile by modifying a numeric user ID in the URL.

2. What are the 5 steps of penetration testing?

The five commonly referenced steps are:

1. Planning & scoping: define goals, scope, and rules of engagement
2. Reconnaissance: gather information about the target app and environment
3. Scanning & vulnerability analysis: use tools and manual checks to find issues
4. Exploitation & post-exploitation: safely exploit vulnerabilities to prove impact
5. Reporting & remediation: document findings, impacts, and fixes, then retest

These align with guidance from frameworks like OWASP WSTG, NIST SP 800-115, and PTES.

3. Is penetration testing manual or automated?

Penetration testing is primarily manual, supported by automation:

• Tools help with:
  
  • Scanning
  • Fuzzing
  • Repetitive tasks
    
• Humans provide:
  
  • Strategy
  • Creativity
  • Understanding of business logic and chain attacks
    

Purely automated “pen tests” are usually just vulnerability scans, not true penetration testing.

4. Is penetration testing black box or white box?

It can be black-box, white-box, or grey-box:

• Black box: No internal knowledge; mimics an external attacker.
• White box: Full access to source, architecture, and credentials; ideal for deep security review.
• Grey box: Limited knowledge; mirrors a partially informed attacker (e.g., stolen credentials).

The right choice depends on your goals, risk profile, and time constraints.

5. What are 3 common types of penetration tests for software?

Three very common types are:

1. Web application penetration testing: web apps, portals, admin consoles
2. API penetration testing: public and internal APIs (REST, GraphQL, etc.)
3. Mobile app penetration testing: Android and iOS apps plus their backends

Most modern organizations start with these before expanding into cloud and infrastructure pen testing.

6. How often should penetration testing be done?

A practical baseline is:

• At least once per year for critical internet-facing applications
• Before major releases or architectural changes
• More frequently (e.g., every 6 months or per major release) for highly regulated or high-risk systems

Combine this with continuous scanning and monitoring so you’re not relying on a once-a-year snapshot.

7. Is penetration testing required for compliance?

Many frameworks expect or strongly recommend regular security testing:

• PCI DSS (for payment systems) requires frequent testing of systems handling card data.
• ISO 27001 and similar standards expect risk-based security assessments, which often include pen testing.
• Sector regulations (finance, healthcare, government) frequently call out penetration testing in guidance.

Even when not strictly mandated, pen testing is often the most convincing form of evidence that security is taken seriously.