Data Exfiltration by Malware: Detection and Analysis Techniques

When completing your malware analysis assignments, understanding the intricacies of malware behavior and analyzing its impact on a system can be challenging. This guide is designed to equip students with the knowledge and tools needed to effectively analyze and solve their programming assignments. It focuses on general principles and methodologies that apply to various types of malwares, providing a structured approach to both static and dynamic analysis.

Malware analysis involves examining malicious software to understand its functionality, behavior, and potential impact on a system. The process includes dissecting the malware code, observing its actions in a controlled environment, and documenting findings. This comprehensive approach helps in identifying how malware operates, its persistence mechanisms, and its interactions with the system.

By mastering these techniques, students will be better prepared to tackle malware analysis tasks in their programming assignments. The ability to detect and analyze data exfiltration by malware is a critical skill in cyber security, offering insights into how malware steals data and evades detection. This guide provides the foundation for developing these essential skills.

Introduction to Malware Analysis

Malware analysis involves dissecting malicious software to understand its functionality, behavior, and potential impact on a system. Assignments in this area often require you to perform static and dynamic analysis to uncover how malware operates, its persistence mechanisms, and its interactions with the system. Here’s how to approach such assignments systematically.

1. Initial Overview: Understanding the Malware

Executive Summary

Begin by thoroughly reviewing the assignment brief. This will typically include a description of the malware’s behavior, its purpose, and its impact. For instance, if the assignment involves malware that encrypts a user’s hard drive and demands a ransom, your task will be to analyze how it achieves this encryption and maintains persistence.

Identifying Key Components

File System Changes: Determine which files and directories the malware creates or modifies. For example, the malware may create a directory like C:\DC22 and populate it with various executables and DLLs.
Registry Modifications: Identify any registry keys or values that the malware adds or changes. This is crucial for understanding how the malware maintains persistence or establishes its presence on the system.

2. Static Analysis: Dissecting the Code

Static analysis involves examining the malware without executing it. This method provides insights into the malware’s structure, imported libraries, and key functionalities.

Using Tools: PEStudio and Ghidra

1. PEStudio Analysis:

Compilation Date: Look at the compilation date to understand when the malware was created. This can provide context about its development.
File Characteristics: Check if the malware is packed. Packed files often have high entropy, indicating compression. Use entropy values to determine if the malware is packed.
Sections: Examine different sections (.text, .data, .rsrc) to understand the code structure and resource usage.

2. Ghidra Analysis:

Decompilation: Use Ghidra to decompile the malware and analyze its code. Focus on the main function and its execution flow.
Imports and Functions: Identify imported libraries and functions. Suspicious functions related to file operations, process creation, or service management can indicate malicious behavior.

Example Analysis Steps

Check Entropy Levels: If the entropy is normal (e.g., around 6.365), the file is likely not packed. If entropy is high, the file might be packed, requiring unpacking to analyze further.
Review Section Data: Analyze sections for embedded resources or code. Pay attention to strings that might reveal paths, commands, or network activity.

Dynamic Analysis: Observing Behavior

Dynamic analysis involves running the malware in a controlled environment to observe its behavior. This helps confirm static analysis findings and provides practical insights into the malware’s operations.

Setting Up a Controlled Environment

Virtual Machine: Use a clean virtual machine (VM) to ensure the malware does not affect your primary system.
Monitoring Tools: Utilize tools like Regshot, Process Monitor, and APIMonitor to track changes made by the malware during execution.

Example Steps for Dynamic Analysis

Initial Execution: Run the malware with different arguments to observe its behavior. Check for file creation, registry changes, and system modifications.
Service Creation: If the malware creates a service, confirm its persistence mechanism. For instance, check if it registers a service to run automatically at startup.
Reboot and Restart: Observe system changes after rebooting. Verify if the malware’s service starts automatically and if the system behavior matches the expected patterns.

Analyzing Persistence Mechanisms

Persistence mechanisms allow malware to remain active across system reboots. Common methods include creating services, modifying registry keys, and scheduling tasks.

Identifying Persistence Techniques

Services: Check for new services created by the malware. For example, a service might be named DefragmentService and configured to run the malware executable.
Registry Keys: Look for registry keys related to the malware’s services or drivers. Keys like HKLM\SYSTEM\CurrentControlSet\services can reveal service configurations.
Scheduled Tasks: Some malware creates scheduled tasks to execute payloads periodically.

Encryption and Data Exfiltration

Malware that encrypts data or exfiltrates information requires specific analysis techniques to understand its impact.

Encryption Analysis

Identify Encryption Methods: Determine if the malware uses known encryption tools (e.g., DiskCryptor) or custom algorithms.
Analyze Encryption Process: Review how the malware performs encryption. Check for command-line arguments or configuration files that specify encryption parameters.