A No-Nonsense Guide to Penetration Testing Types and Approaches

When we talk about penetration testing, think of it as hiring experts to try and break into your computer systems—similar to having professionals test the security of your house. Understanding the different testing methods allows you to choose the right approach to protect your company’s assets.

The Six Types of Penetration Testing

Here’s a look at how ethical hackers assess your security from various angles, much like checking all the points of entry into a building.

1. External Testing (From the Outside)

This approach examines everything visible from the internet—your websites, email servers, and other public-facing infrastructure. It reveals the vulnerabilities an external attacker might target first. Because it mimics what an average cybercriminal might see, many companies begin with external testing.

2. Internal Testing (From the Inside)

Imagine someone has already bypassed your initial security defenses. Internal testing looks at your internal networks, shared drives, and devices to determine what a hacker could access once they’re inside your system. It often uncovers unexpected vulnerabilities, such as poorly secured servers or weak internal protocols.

3. Web Application Testing

Since many companies build their business on web platforms, testing your websites and applications is essential. In web application testing, experts use techniques like SQL injection (inserting unauthorized commands into web forms) or cross-site scripting (injecting malicious code into web pages) to expose vulnerabilities. This is especially important for businesses handling sensitive user or financial data.

4. Social Engineering Testing

People can be the weakest link in any security system. In social engineering tests, experts use tactics such as phishing (sending deceptive emails), impersonating IT support, or even attempting entry into premises using fake credentials. This testing highlights how human factors can sometimes bypass technical security measures.

5. Wireless Testing

With increasing reliance on wireless devices, it’s critical to test your WiFi networks and Bluetooth connections. Testers examine these channels to ensure that attackers can’t gain easy access to your network from outside—whether it’s from a nearby location or a public area.

6. Physical Testing

In some cases, penetration testing goes beyond digital methods. Physical testing involves assessing the effectiveness of your building’s security—for example, checking if someone can tailgate through secure doors, pick locks, or retrieve sensitive documents from discarded materials. This type of testing evaluates both your physical defenses and employee awareness.

How Much Information Do You Provide?

The amount of background information you share with testers affects their methods and the insights they can gather. Here are the three main levels:

Black Box – Testing as an Uninformed Attacker

Testers receive no prior information about your systems, simulating a real attacker’s perspective. They must discover vulnerabilities on their own. This method closely mirrors real-world attacks but is often time-intensive and might not uncover every potential issue.

Gray Box – Testing with Limited Knowledge

In a gray box test, testers are given some information (similar to what an insider might know). This balanced approach helps them identify serious vulnerabilities while maintaining a degree of realism. It’s one of the most popular choices for comprehensive, routine security assessments.

White Box – Testing with Full Access

For white box testing, testers are provided complete access, including source code, network diagrams, and system documentation. While this isn’t typical of external attack scenarios, it enables a detailed audit of your systems to identify deeper security issues.

Choosing Your Testing Strategy

Effective security testing often combines multiple approaches based on your specific risks and business needs. For example, an EdTech company may prioritize web application testing to secure student data, while also scheduling frequent social engineering assessments to ensure employees remain vigilant.

A good starting point is to combine external and web application testing since these address your most publicly exposed assets. Over time, you can expand to include internal, social engineering, wireless, and physical testing as your security program matures.

Remember, the goal of penetration testing isn’t just to find vulnerabilities—it’s to discover and address them before actual attackers can exploit them.