What Is a Penetration Test? Complete Guide for Founders and CTOs
What Is a Penetration Test? Complete Guide for Founders and CTOs
TLDR: A penetration test is a structured, authorised attempt to break into your systems before an attacker does. It's not an automated scan — it's a skilled professional thinking and acting like an adversary against your real environment. This guide covers what a pen test actually involves, the different types, what a good report looks like, what it costs, and the red flags to watch for when hiring someone to do one.
The Most Common Question I Get From Startup Founders
It usually comes after a funding round, a customer security questionnaire, or a close call with a suspicious login. The question is almost always the same: "We need a pen test — but I don't really know what that means. Where do we start?"
It's a good question, and it doesn't have an obvious answer if you've never been through the process. This guide is my attempt to answer it thoroughly, so that by the time you finish reading it you know exactly what you're buying, what to expect, and what to watch out for.
What a Pen Test Is — and What It Isn't
A penetration test is an authorised, simulated attack on your systems, applications, or infrastructure. A skilled tester — working within an agreed scope and timeframe — uses the same tools, techniques, and thinking as a real attacker to find vulnerabilities before one does.
What it is not: a vulnerability scan. Automated scanners crawl your application and flag known issues against a database of CVEs. They're useful, fast, and miss a great deal. A pen tester uses tools like that as a starting point, then manually investigates, chains vulnerabilities together, tests business logic, and finds the things automated tools are structurally incapable of finding — like a flawed password reset flow, a broken multi-step process, or a privilege escalation that only emerges when you combine three low-severity findings.
A pen test produces a point-in-time snapshot. It tells you what your security posture looked like during the test window. It is not continuous monitoring, and it is not a guarantee — it's intelligence.
Types of Penetration Testing
Web Application Testing covers your customer-facing and internal web apps — authentication, authorisation, input handling, session management, API security, and business logic. This is the most common engagement for startups and SaaS companies.
Network Testing examines your internal or external network infrastructure — open ports, exposed services, misconfigured firewalls, and lateral movement opportunities within a corporate environment.
Social Engineering Testing assesses your human layer — phishing simulations, vishing calls, and physical access attempts to understand whether your people and processes hold up against a determined attacker. We covered this in detail in our post on social engineering.
Cloud Security Testing reviews your cloud environment — AWS, GCP, or Azure — for misconfigurations, overpermissioned roles, exposed storage buckets, and insecure infrastructure-as-code. Cloud misconfigurations are now among the most common causes of significant data breaches.
Black Box, Grey Box, and White Box
These terms describe how much information the tester starts with.
Black box — the tester knows nothing about your internal systems. They start from the same position as an external attacker. Realistic, but slower and less thorough, since significant time is spent on reconnaissance that you could have provided upfront.
Grey box — the tester has partial information: perhaps a user account, basic architecture documentation, or access to certain environments. This is the most common and usually most cost-effective approach for web application testing — realistic enough to surface real risks, efficient enough to go deeper.
White box — the tester has full access: source code, architecture diagrams, credentials, documentation. This produces the most thorough results and is particularly valuable for code-heavy products where you want the assessment to go as deep as possible.
For most startups, grey box web application testing is the right starting point.
The 5 Phases of a Penetration Test
1. Scoping and planning. The engagement is defined — what systems are in scope, what types of testing are permitted, what the timeline is, and what the rules of engagement are. A signed authorisation document is non-negotiable before anything begins.
2. Reconnaissance. The tester gathers information about the target — publicly available data, technology fingerprinting, identifying entry points. For external testing, this mirrors exactly what an attacker would do before launching an attack.
3. Exploitation. Identified vulnerabilities are actively exploited to determine real-world impact. Can the SQL injection actually extract data? Does the broken access control lead to account takeover? This is where the test moves beyond theory.
4. Post-exploitation. Once access is gained, the tester assesses what an attacker could realistically do from that position — lateral movement, privilege escalation, data exfiltration. This determines the true business impact of each finding.
5. Reporting. Every finding is documented with: what it is, how it was found, what an attacker could do with it, the severity rating, and specific remediation guidance. The report is the deliverable you take back to your team.
What a Good Report Includes
A good pen test report has two audiences: your technical team and your leadership. It should serve both.
For leadership: an executive summary that describes the overall risk posture in plain language, the most critical findings, and the business impact — without requiring a security background to understand.
For the technical team: detailed reproduction steps for each finding, the exact payloads or methods used, screenshots, severity ratings using a recognised framework like CVSS, and specific, actionable remediation guidance — not "fix your access controls" but "implement ownership validation on line 47 of UserController.php."
If a report you receive doesn't include both, ask for them. A report you can't act on is not a report worth paying for.
What to Do With the Results
Triage by severity first. Critical and high findings should be scheduled for remediation immediately — before the next release if possible. Medium findings should be sprint-planned. Low and informational findings should be logged, prioritised against other engineering work, and addressed over time.
Book a debrief call with the testing team. Good pen testers will walk through their findings, answer technical questions, and confirm whether proposed fixes actually address the root cause. This conversation is often more valuable than the report itself.
Once critical findings are remediated, retest them. Most reputable firms include free retesting of critical findings within a defined window — confirm this before you sign.
What Does It Cost?
Pricing varies significantly by scope, type, and provider. As a realistic range for 2025–2026:
A web application pen test for a mid-sized SaaS product typically runs between roughly $1,000 – $3,500 USD depending on the number of endpoints, complexity, and testing depth.
A comprehensive engagement covering web app, API, and cloud infrastructure for a funded startup is typically in the range $3,000 – $8,500 USD.
Prices at the lower end of the market are usually automated scans dressed up as manual testing. Prices at the high end from large consultancies often reflect overhead rather than quality. The right question isn't "what's the cheapest pen test?" — it's "what will I actually learn, and can I act on it?"
If you want a specific quote based on your actual scope, get in touch and we'll scope it properly.
Red Flags When Hiring a Pen Tester
Watch out for any firm that: delivers a report within 24–48 hours of a multi-system engagement (not enough time for real manual testing), can't explain their methodology in plain language, won't sign a scope-and-authorisation document before starting, produces reports that read like raw scanner output with no manual analysis, or can't provide a sample report or client reference on request.
A real pen test takes time, judgment, and expertise. Anyone offering a comprehensive test at a price that seems impossible should be asked to explain exactly how they'll spend that time.
Ready to Start? Here's How to Work With Us
At Kuboid Secure Layer, we scope every engagement individually — we don't sell off-the-shelf packages because every application and business is different. If you're not sure what type of test you need, that's a normal starting point and we're happy to help you figure it out.
You can explore our services, learn more about us, or go straight to getting in touch. The first conversation is always a scoping discussion, no obligation.
More guides like this are available on the Kuboid Secure Layer blog.