Understanding Thick Client Application Penetration Testing

In today’s hybrid work environment, thick client applications are especially susceptible to cyberattacks. Notably, even tech giants like Google and Yahoo have experienced security breaches in their applications. Last month Google released an emergency security update for Chrome version 116 to address a critical zero-day vulnerability (CVE-2023-4863) found in the WebP component. This bug, a heap buffer overflow issue, has the potential for exploitation and is already being used in the wild, as per Google’s advisory.

This incident underscores the significance of thorough security measures, especially in organizations that utilize thick client applications. These applications, which run on end-user devices and communicate with servers or backend systems, demand comprehensive security assessments to safeguard against data breaches and cyberattacks.
Thick client applications, unlike their web-based counterparts, are typically installed directly on a user’s computer. They interact with remote servers to perform various tasks, such as desktop email clients, video conferencing applications, and financial software. However, their unique architecture requires special attention to security. Read on to learn about what thick client penetration testing is, its types, and how it’s carried out. Discover Breachlock’s multi-faceted approach to thick client penetration testing.

Understanding Thick Client Penetration Testing

Thick client applications, also known as desktop applications, are complete computing systems connected to a network. In contrast to thin clients, which typically lack hard drives and other essential features, thick clients maintain their functionality whether they are connected to a network. Thick client penetration testing is an assessment process aimed at evaluating the security of these desktop applications by identifying vulnerabilities, testing authentication mechanisms, assessing data encryption, addressing security misconfigurations, and examining network communication to ensure the robustness and integrity of thick client software.

Thick client applications can be categorized into two-tier or three-tier network architectures, each with its own distinct structure and security considerations. These network models are often referred to as tiered models due to their layered approach.

Three-Tier Architecture

• In a three-tier architecture, the thick client app interacts with the server via an application server.
• It consists of three tiers: presentation, application, and data.
• The end-user interacts with the app in the presentation tier.
• Data processing occurs in the application tier, and data is stored in the data tier.

Two-Tier Architecture

• In a two-tier architecture, there are just two tiers: presentation and data.
• The thick client app connects directly to the server, bypassing the application server.
• This architecture is less secure because the end-user has direct access to the data tier.

Types of Thick Client Penetration Testing Methods

Thick client penetration testing involves various methods tailored to different aspects of application security:

• Source Code Analysis: Examining the application’s source code to identify vulnerabilities and coding errors.
• Binary Analysis: Analyzing the compiled executable file to understand its functionality and uncover security vulnerabilities.
• Reverse Engineering: Deconstructing the application to understand its inner workings, algorithms, and data structures.
• Protocol Analysis: Examining communication protocols to identify potential security weaknesses.
• Runtime Analysis: Monitoring the application’s behavior in real-time to detect vulnerabilities or unexpected activities.

Additionally, input validation and boundary testing are essential to secure thick client applications by identifying and fortifying against potential weaknesses.

How Thick Client Penetration Testing Is Performed?

Thick client penetration testing is carried out in 5 phases. The first phase is the “information gathering” phase; here the focus is on gathering essential data about the thick client application and understanding its purpose, architecture, and technology stack. Automated scanning tools, public resources, and specialized requests are employed to collect information about the application’s endpoints, communication protocols, and dependencies, including third-party libraries.

The next phase is “target mapping”, in which the application’s objectives are comprehensively assessed, considering both legitimate user and potential attacker perspectives. This involves identifying attack surfaces, such as login mechanisms, data storage, communication channels, and API endpoints, while documenting data flows within the application and between the client and server components.

“Discovering Vulnerabilities” follows, with the creation of a test plan to outline various test cases and potential attack scenarios. A rigorous testing process is employed to identify vulnerabilities, including those listed in OWASP’s top 10 for desktop applications, along with other application-specific issues. The OWASP desktop app security top 10 is a comprehensive guide outlining the most critical security risks associated with desktop applications. Here are the ten most common vulnerabilities in thick client applications according to OWASP:

1. DA1 – Injections
2. DA2 – Broken Authentication and Session Management
3. DA3 – Sensitive Data Exposure
4. DA4 – Improper Cryptography Usage
5. DA5 – Improper Authorization
6. DA6 – Security Misconfiguration
7. DA7 – Insecure Communication
8. DA8 – Poor Code Quality
9. DA9 – Using Components with Known Vulnerabilities
10. DA10 – Insufficient Logging and Monitoring

Subsequently, in the “Exploitation” phase, vulnerabilities are tested to determine their severity and potential exploitability. Finally, in “Reporting and Analysis,” a comprehensive report is compiled. It includes detailed descriptions of the identified vulnerabilities, their severity, and potential impacts.

Recommendations for mitigating these vulnerabilities, such as code changes, configuration adjustments, or patches, are provided, with a focus on prioritizing vulnerabilities based on their risk level and potential organizational impact. This report is then shared with relevant stakeholders, including developers, product owners, and security engineers, to guide the necessary actions to address the identified security issues.

BreachLock’s Comprehensive Methodology for Thick Client Penetration Testing

BreachLock’s thick client penetration testing is a comprehensive assessment that holistically evaluates the security of thick client applications. This rigorous examination covers multiple dimensions, encompassing not only the thick client itself but also the network side, server side, offline scenarios, and the thick client’s interaction with end-users.

The primary focus of this assessment is on the thick client application, involving a meticulous analysis of its code, design, and functionality. Vulnerability identification, authentication and authorization testing, data encryption, and the detection and resolution of insecure configurations are key elements in this phase. Additionally, the assessment extends to the client side, aiming to identify and address client-side vulnerabilities that could be exploited by malicious actors.

In parallel, BreachLock also scrutinizes the network communication between the thick client application and the backend server. This includes traffic analysis to uncover any vulnerabilities related to data transmission, an evaluation of susceptibility to Man-In-The-Middle (MITM) attacks, and an assessment of firewall and network configurations to safeguard thick client communications.

The assessment also encompasses an evaluation of end-user behavior and susceptibility to social engineering attacks, which could potentially compromise the thick client application or the associated credentials. Furthermore, secure data handling is a critical aspect, ensuring that sensitive data, such as authentication tokens or cached data, is managed securely on the user’s device.

Lastly, the offline analysis component assesses how the thick client application behaves when it operates in an offline or disconnected state, identifying vulnerabilities that may arise in such scenarios. Altogether, this comprehensive approach ensures that thick client applications are thoroughly tested and fortified against potential security threats, safeguarding both the software and the sensitive data it manages.

About BreachLock

BreachLock is a global leader in PTaaS and penetration testing services. BreachLock offers human-delivered, AI-powered solutions integrated into a single platform based on a standardized built-in framework that enables consistent and regular benchmarks of attack tactics, techniques, and procedures (TTPs), security controls, and processes to deliver enhanced predictability, consistency, and accurate results in real-time, every time.
Schedule a discovery call with our experts to learn how BreachLock can help your organization in thick client penetration testing.