How well one's own defenses really hold up only becomes clear when someone seriously tries to overcome them. That is exactly what a penetration test achieves: security professionals attack a company's systems on its behalf, in a controlled way and with clear limits. For IT decision-makers, it is one of the most honest testing instruments, because it replaces assumptions with evidence.
What is a penetration test?
A penetration test (pentest for short) is a commissioned security assessment in which professionals try to break into systems and applications using the methods of real attackers. The goal is a practical proof: which vulnerabilities exist, can they be exploited, and what damage would be possible in an emergency? From the answers, prioritized recommendations for remediation emerge.
According to the testers' level of knowledge, three variants are distinguished. In a black-box test, the testers start without prior knowledge and see the target like an external attacker. In a grey-box test, they receive partial information, such as a user account or a network overview. In a white-box test, the architecture, configurations, or source code are disclosed, which allows the greatest depth of testing.
In addition, the test object differs: external tests examine systems reachable from the internet, such as VPN gateways or customer portals. Internal tests simulate an attacker who already stands within the company network, for example after taking over a workstation computer. Tests of web applications concentrate on authentication, session management, input validation, and business logic.
Legally, the following applies: a pentest needs a written engagement and the express permission of the system owner. Without this basis, intruding into third-party systems is a criminal offense in Germany. If systems are located with cloud or hosting providers, their rules for security tests must additionally be observed and affected third parties involved.
How does a penetration test proceed?
Reputable tests follow a structured approach in five steps:
- Scoping and engagement: Client and testers define goals, systems, time windows, testing depth, and off-limits zones. The written engagement governs permission, liability, confidentiality, and emergency contacts in case the test affects productive systems.
- Information gathering: The testers collect knowledge about the target, from publicly available information to active reconnaissance of reachable services and software versions.
- Vulnerability analysis: Tool-supported checks and manual analysis complement each other. The testers assess which findings can be combined into realistic attack paths.
- Exploitation: Selected vulnerabilities are exploited in a controlled way to prove actual access. This includes privilege escalation and the question of how far an attacker could move within the network.
- Report and debrief: The final report documents every finding with proof, risk assessment, and a concrete recommendation, supplemented by a summary for management. A retest after remediation checks whether the measures work.
Why a penetration test matters
- It proves which vulnerabilities can be exploited in practice, instead of stopping at theoretical lists.
- It checks, along the way, whether monitoring and alerting notice an ongoing attack at all.
- It makes risks tangible for management and budget planning, because attack paths are described concretely.
- Customers, auditors, insurers, and supervisory authorities increasingly demand evidence of conducted security tests.
- It finds classes of errors that automated tools overlook, such as logic errors in applications or risky combinations of individual weaknesses.
Typical scenarios
- Before the go-live of a customer portal, an external test including the web application checks whether login and data access hold up.
- An internal test answers the question of how far an attacker would get after taking over a single workstation, a realistic ransomware scenario.
- After an acquisition, a pentest assesses the inherited infrastructure before the networks of both companies are connected.
- Recurring tests serve as proof of effectiveness within an information security management system.
- After a major release, a renewed test of the web application checks whether new functions have opened new gaps.
Penetration test vs. vulnerability scan
A vulnerability scan works automatically: it compares systems against databases of known vulnerabilities, runs frequently and comprehensively, but assesses neither exploitability nor context. A penetration test starts exactly there: people chain individual weaknesses into real attack paths and prove the effects. Both belong together: continuous vulnerability management keeps the attack surface permanently small, the pentest checks selectively in depth. AI is shifting the pace in both fields: attackers automate reconnaissance and exploit development, testers speed up analysis and reporting. Our glossary entry on Mythos sheds light on how far autonomous AI systems have come in offensive security.
Working with KAEMI
KAEMI does not conduct penetration tests itself. As a managed service provider for secure corporate networks, we apply ourselves where many test reports identify the greatest risks: at open internal networks and unchecked lateral movement. With Zero Trust microsegmentation , we close exactly the paths over which testers and real attackers work onward from a first system. For exposed web applications, Application Security reduces the attack surface even before the next test. In this way, a pentest report turns into a permanently harder network. Get in touch via our contact form if you would like to translate findings into effective measures.