In today’s digital world, cybersecurity has become a top priority for businesses. Every day, organizations face cyberattacks that can expose sensitive data, disrupt operations, and cause significant financial losses.
In 2025 alone, the US reported a record 3,322 data breaches, affecting more than 278 million people. Most attacks involved phishing, third-party service vulnerabilities, exposed APIs, ransomware, and increasingly, AI-related security breaches. About 13% of organizations reported compromises involving AI models.
To detect security weaknesses and vulnerabilities, many large companies perform an authorized simulated cyberattack on their own system. This is what we call penetration testing (Pen Test for short). Basically, the aim is to identify security vulnerabilities and weaknesses before a cyberattacker exploits them and fix them as soon as possible.
More specifically, penetration testing involves simulating real-world attack scenarios to find and exploit security gaps (in a safe manner) that could ultimately lead to stolen information, compromised credentials, or other harmful business outcomes.
It can be performed either in-house using a pen-testing tool or outsourced to a penetration testing provider. The process usually begins with a security professional enumerating the target network to detect vulnerable devices or accounts. This means scanning every device on the network for open ports that have services running on them.
The level of intrusion depends on the type of operation the security tester wants to explore on the target system. Therefore, the tester must have a good knowledge of the most relevant kind of pen test.
Penetration tests can be classified by how they are performed and by the assets and components targeted. In this overview article, we have explained different types of penetration testing that are designed to be intense and invasive.
Table of Contents
Penetration Testing Based On Methods Used
1. Black Box Testing
- Test cases can be designed immediately
- Can detect a certain kind of flaws
In black-box penetration testing, the tester doesn’t have access to the client’s application, network configuration, or any kind of internal information. He/she performs all reconnaissance to extract the required information.
This type of testing determines the weaknesses of a system that are exploitable from outside the network. Finding those weaknesses relies on dynamic inspection of currently running programs and systems within the target network.
A penetration tester should be skilled in both automated security scanning tools and manual testing techniques. Since black box testing provides no access to system configurations or source code, the tester must identify vulnerabilities by exploring the target system and building a map of the network through observation and analysis.
Limited knowledge prevents the tester from identifying all vulnerabilities in the system. This is the major downside of this type of testing. If testers can’t breach all perimeters, internal vulnerabilities remain undiscovered.
However, it can uncover certain kinds of flaws, such as server configuration mistakes and input/output validation errors. To be successful (efficiently detect and remediate more vulnerabilities), black-box testing methodologies should be combined with other testing tools.
There are plenty of tools available in the market for conducting black-box penetration testing. Wapiti, for example, analyses web applications for potential liabilities by injecting temporary data.
2. White Box Testing
- More Comprehensive
- Allows for code optimization and detection of hidden security issues
As the name suggests, white box penetration testing is the opposite of black-box testing. The tester has complete access to architecture documentation, source code, and other system information.
Testers sift through a large volume of data available to detect potential points of weakness. They can use both static and dynamic code analyzers and debuggers for this kind of testing.
Since testers have complete knowledge of the system, they need more time to plan the assessment. They must decide which modules to test first and choose the most suitable tools and techniques for each part of the system.
JUnit, PyUnit, and Selenium are some of the most popular open-source white-box testing tools. Selenium, for instance, is used for validating web applications across various browsers and platforms.
3. Gray Box Testing
- Identifies more significant vulnerabilities with less cost and effort
- Testing is performed from the users’ point of view instead of the designer’s
This is a combination of black-box and white-box penetration testing. The gray box pen tester has some knowledge of the system’s internals, such as the database and design documents. With this limited knowledge, he/she can make better test data and test cases while preparing a test plan.
This type of testing provides a more efficient and focused assessment of the system’s security compared to a black-box assessment. It can identify defects caused by improper application use or improper code structure. More specifically, it uncovers the context-specific errors by concentrating on all layers of complex systems.
Gray box testing is better suited to functional testing, web applications, web services, security assessments, and GUIs. Burp Suite is a popular gray-box testing tool that exploits application vulnerabilities by targeting potentially insecure spots.
Differences Between These Three Testing Techniques
| Black Box Penetration Testing | Gray Box Penetration Testing | White Box Penetration Testing |
| No knowledge of the system’s internal workings is required | Partial knowledge of the system’s internal workings is required | Complete knowledge of the system’s internal workings is required |
| Very difficult to discover hidden errors | Difficult to discover hidden errors | Simple to discover hidden errors |
| Also known as closed-box testing or data-driven testing | Also known as translucent testing | Also known as clear-box testing, structural testing, or code-based testing |
| Least time-consuming | Partly time-consuming | Most comprehensive and time-consuming |
| Best for finding input/output validation errors | Best suited for testing data domains and system design | Best suited for testing algorithms, code structure, and internal boundaries |
| Tests are conducted by end-users, developers, and testers | Tests are performed by independent testers and developers | Tests are performed by testers and developers |
Penetration Testing Based On Targeted Components
1. Network Services Testing
- Prevents network and data breaches
- Ensures network and system security
The network penetration testing process involves discovering security vulnerabilities in applications and systems by using various malicious methods to assess network security.
Typically, the tester identifies exploitable networks, hosts, systems, and devices (such as switches and routers) to uncover weaknesses. Since a network has both external and internal access points, it is mandatory to perform tests remotely from the outer world and locally at the client site.
This helps testers understand the level of risk the organization is dealing with and how to address and fix security flaws. Depending on the risk, they can target different network areas in their tests. For example, they can conduct:
- Stateful analysis testing
- Firewall config testing
- Firewall bypass testing
- DNS attacks
The most common protocols investigated in these tests include:
- Simple Mail Transfer Protocol (SMTP)
- File Transfer Protocol (FTP)
- Secure Shell (SSH)
- MySQL and SQL Server
Depending on the system’s size and complexity, it may take anywhere from one to four weeks to complete a network penetration test. Testers can offer a detailed estimate only after scoping the project.
2. Web Application Pen Testing
Steps to perform a web app pen test
- Identifies vulnerability in both design and configuration
Locates intruders and blocks them
Since many web applications hold sensitive information, it is necessary to keep them secure at all times. One way to do that is to include web app penetration testing as a part of the Software Development Life Cycle (SDLC).
Pen tests make it easy to identify vulnerabilities across the entire web application and its components, including the database, backend network, and source code. This helps developers pinpoint and prioritize weaknesses and errors and develop ways to mitigate them.
This type of testing involves collecting data on the target web app, mapping the host network, and examining all possible points of injection or tampering. The main reasons for performing web app pen testing are:
- Detect unknown vulnerabilities
- Check publicly exposed components, such as routers and firewalls
- Find the most vulnerable route for a possible attack
- Look for loopholes that could result in information theft
- Check the effectiveness of existing security policies
Plenty of tools are available on the market to conduct (both manual and automated) web app penetration testing. Vega, Veracode, and Zap are among the most common for quick tests.
3. Wireless Pen Testing
- Determines the realistic security posture of wireless networks
- Addresses vulnerabilities and security policies/procedures
Wireless penetration testing involves detecting and analyzing the connections between all devices connected to the business’s WiFi. This includes laptops, smartphones, tablets, printers, and other Internet of Things (IoT) devices.
Wireless penetration testing examines Wi-Fi networks, wireless protocols, and access points to identify security weaknesses. Since the tester must be within range of the wireless network, these assessments are usually performed at the client’s location.
Common vulnerabilities include weak Wi-Fi configurations, missing MAC address filtering, and inadequate network access controls. Regular testing helps organizations identify and fix these weaknesses before attackers can exploit them.
It’s also important to keep in mind that WiFi is not the only wireless technology attackers can exploit. There are several Bluetooth devices, Bluetooth Low Energy devices, and other less popular technologies, such as Z-wave and DECT (cordless phone), found in public.
4. Client-Side Penetration Testing
- Detects security misconfigurations in client-side software
- Allows proper control of inbound and outbound network traffic
This is an internal Pen Test where testers exploit vulnerabilities in client-side application programs such as web browsers, Adobe Acrobat, email clients, Macromedia Flash, etc.
While there is no rule for conducting such tests on specific intervals, businesses should perform pen tests when new IT infrastructure or client-side applications are added or when existing infrastructure is altered.
Most client-side vulnerabilities stem from unpatched software installed on laptops or desktops. Some attackers even intercept the updating process, sending malicious code along with the original update.
Attackers often use USB devices to spread malware or malicious programs. Once an infected USB drive is connected to a computer, the malicious code may run automatically or trick the user into executing it. Other common client-side attacks include cross-site scripting (XSS), form hijacking, clickjacking, HTML injection, and open redirects.
This is why it is important to test employees’ susceptibility and networks’ capability to recognize and respond to client-side attacks.
5. External Pen Testing
- A security assessment of a company’s perimeter systems
- Includes both application-layer and network-layer assessments
External penetration testing generally tests from the attacker’s perspective with no prior access to the target system or network. This is different from internal pen testing, in which the attacker already has a foothold on the compromised machine.
In external penetration testing, the tester attempts to access an organization’s internal network by exploiting vulnerabilities in internet-facing systems. The process begins with reconnaissance, where the tester gathers information about all assets within the defined scope.
This data may include open ports, vulnerabilities, or employees’ information for password attacks. Once the perimeter is breached, the external penetration test is complete, and the tester proceeds to internal pen testing.
6. Social Engineering
- Con unsuspecting employees into compromising the company’s security
- Exploit human psychology to get confidential data
The term social engineering is used to describe a wide range of malicious activities carried out through human interactions. Since it relies on human error (instead of weakness in applications or networks), it is less predictable and harder to detect than malware-based intrusions.
These kinds of tests involve attempting to get confidential data by tricking the company’s employees into revealing sensitive information. This could be achieved through either remote testing or physical testing.
Remote testing involves sending phishing emails to employees or bombarding their devices with false alarms or fictitious threats. In contrast, physical testing includes tailgating, impersonation, dumpster diving, and physical threats.
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