Information Gathering
Unlike web applications, thick-client apps often operate in closed environments with complex internal workings. They may communicate over proprietary protocols, store sensitive data locally, or integrate deeply with the host operating system. Without thorough reconnaissance, testers risk missing critical vulnerabilities hidden within these layers.
The core goal is to map out the application's internals—its architecture, dependencies, data flows, and communication channels—so that targeted and effective exploits can be devised.
Key Objectives of the Phase
Application Architecture: Determine whether the application is standalone, two-tier, three-tier, or employs Service-Oriented Architecture (SOA). This influences testing strategies—local exploits vs. network-based attacks.
Platform Mapping: Identify the operating system (Windows, Linux, macOS), architecture (32/64-bit), and runtime environment (e.g., .NET, Java, Electron).
Languages & Frameworks: Detect programming languages and frameworks used (C#, Java, Python, .NET, Electron) to tailor reverse engineering and decompilation efforts.
Dependencies & Components: Map external libraries, DLLs, and modules to uncover outdated or vulnerable components.
Communication Protocols: Identify network protocols and endpoints—be they HTTP/S, TCP, UDP, or proprietary protocols—and associated IP addresses and ports.
Data Storage: Locate local data stores such as files, registry keys, or databases that may harbor sensitive information.
User Roles & Data Flows: Understand permissions, authentication mechanisms, and data flow to identify potential privilege escalation points or data leakage.
Techniques & Tools for Effective Information Gathering
1. Binary Analysis with CFF Explorer
Understanding the binary structure of the application reveals vital clues about its build environment, language, and dependencies. Using CFF Explorer, analysts can:
Load the executable file.
Inspect the PE (Portable Executable) header.
Determine whether it’s a native C/C++ app or a .NET assembly.
Identify imported libraries and functions.
Commands & Steps:
Example:
Loading BetaFast.exe reveals it's a 32-bit .NET assembly built with Visual Studio, indicating decompilation with DnSpy.
2. Dependency & Framework Detection with Detect It Easy (DIE)
Quickly determining the file type, packers, and frameworks helps plan further analysis.
Commands & Steps:
Sample output:
Use: Confirming it's a .NET assembly guides you to use DnSpy for decompilation.
3. System Integration & Network Mapping with Sysinternals Suite
Windows applications often register services or establish network connections. TCPView helps visualize this.
Commands & Steps:
Filter for your process:
Example:
DVTA.exe connects to 192.168.1.100:443 over TCP, indicating server communication.
4. Network Traffic Analysis with Wireshark
Capture and analyze network packets to uncover plaintext data or weak encryption.
Commands & Steps:
Select the relevant network interface (e.g., Ethernet or Wi-Fi).
Apply display filters:
Start capturing, then log into the application.
Right-click a packet and select:
Example:
The TCP stream shows a login request transmitting credentials in plaintext (username=ashok&password=secret).
5. Monitoring with Process Monitor (Procmon)
Procmon tracks real-time system activity.
Commands & Steps:
Set filter for your process:
Run the application and observe activities.
Look for registry keys:
Inspect events like:
Use: Modify registry entries to manipulate sessions or credentials.
6. Additional Techniques
File System Enumeration:
Memory Dumping:
Auto-Start & Service Mapping:
User Role & Access Control:
Use Frida to hook into functions:
(where script.js contains custom hooks to analyze role-based logic)
Proprietary Protocols:
Use Echo Mirage to insert into process memory and analyze custom communication formats.
Challenges & Considerations
Data Visibility: Local storage (registry, files) often requires reverse engineering to uncover secrets.
Proprietary Protocols: Custom protocols may need dedicated reverse engineering.
Client-Side Validation: Can be bypassed with manual input or hooking tools.
Offline Functionality: Local files or databases may contain vulnerabilities even when offline.
Expected Outcomes
From thorough reconnaissance, you can expect to uncover:
The application's architecture (standalone, multi-tier, SOA).
Platform details (Windows 10/11, 32/64-bit, runtime).
Dependencies and their versions.
Communication endpoints (IP addresses, ports, protocols).
Local data storage locations.
Vulnerabilities such as plaintext credentials, session management flaws, or misconfigured registry keys.
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