Introduction to Malware Analysis

Malware analysis is the process of understanding the behavior, origin, and impact of malicious software. As cyber threats evolve, organizations and security researchers must continuously analyze and mitigate the risks posed by malware. From uncovering how malware infiltrates systems to developing robust defense mechanisms, malware analysis plays a crucial role in cybersecurity.

In this blog, we’ll explore the fundamentals of malware analysis, various malware types, methodologies used in analysis, and advanced techniques employed by cybercriminals. Whether you’re a beginner or an experienced analyst, this guide offers insights into the world of malware research and detection.

What is Malware?

Malware, short for malicious software, refers to any software designed to disrupt, damage, or gain unauthorized access to computer systems. It’s been a cybersecurity concern since the early days of computing, evolving into sophisticated threats targeting individuals, businesses, and governments.

The primary objectives of malware include stealing sensitive data, spying on user activity, disrupting services, and demanding ransom payments. Infamous attacks like WannaCry and Emotet have caused widespread damage, underscoring the need for effective analysis.

Examples of Malware in Action

Think of malware as a digital burglar—it sneaks in, manipulates your data, and tries to stay hidden. A Trojan horse, for instance, might disguise itself as a legitimate app while secretly recording keystrokes or exfiltrating credentials. Fun fact: if "we" were malware—just joking—it’d be a sneaky piece of software snagging your credentials!

Why Analyze Malware?

• Identifying Cyber Threats: Determine behavior, infection methods, and potential damage.
• Developing Security Measures: Create detection signatures and antivirus definitions through reverse engineering.
• Threat Intelligence: Gain insights into cybercriminal tactics for future defense.

Types of Malware

Common Types

• Viruses: Self-replicating programs that modify other files and spread across systems.
• Worms: Standalone malware that spreads automatically via networks.
• Trojans: Disguised as legitimate software to trick users into executing harmful payloads.
• Ransomware: Encrypts data and demands ransom—decryption only after the attacker’s paid!
• Rootkits: Deeply embedded to hide malicious activity.
• Fileless Malware: Operates in memory without leaving traditional file traces.

Advanced Techniques

• Polymorphic Malware: Changes its appearance or obfuscates code to evade detection.
• Metamorphic Malware: Rewrites its code completely while maintaining functionality.

Basic Malware Analysis Methodologies

Static Analysis

Static analysis involves examining malware without executing it, revealing its structure and functionality through code and resources.

• Inspecting PE Header: Analyzes the Portable Executable (PE) format to reveal metadata.
• Extracting Strings: Identifies hardcoded URLs, file paths, and commands.
• Analyzing Import/Export Tables: Reviews API calls to understand capabilities.

Tools like PE Explorer, IDA Pro, and Ghidra are key for static analysis. For example, extracting strings might reveal a command-and-control (C2) server address.

Dynamic Analysis

Dynamic analysis runs malware in a controlled environment (e.g., sandbox) to observe its real-time behavior safely.

• Virtual Machine Execution: Monitors in a sandbox like Cuckoo Sandbox.
• System Changes: Tracks file modifications, registry changes, and more.
• Network Analysis: Uses Wireshark or Process Monitor to capture C2 communication.

For instance, running malware in Cuckoo Sandbox can expose network connections or data exfiltration attempts.

Deep Dive: Windows APIs and Malware Interaction

Malware often leverages Windows APIs to manipulate processes, memory, and system settings.

Process Management APIs

• CreateProcess: Launches hidden scripts (e.g., a PowerShell script for persistence).
• OpenProcess: Enables code injection into running processes.
• TerminateProcess: Kills security tools or competing malware.

Memory Manipulation

• VirtualAlloc: Allocates memory for storing malicious payloads.
• ReadProcessMemory: Reads data from other processes.
• WriteProcessMemory: Injects code into target processes.

DLL Injection Techniques

DLL injection forces a legitimate process to load a malicious DLL:

• Remote Thread Injection: Creates a thread in a remote process.
• Reflective DLL Injection: Loads a DLL into memory without disk writes.

Example: Injecting into explorer.exe to evade security software.

Registry Manipulation

• RegCreateKeyEx: Creates registry keys for persistence.
• RegSetValueEx: Sets values (e.g., under `Run` for auto-start).

Understanding the Portable Executable (PE) File Format

The PE file format is central to Windows malware:

• Headers: Contain metadata and entry points.
• .text Section: Stores executable code.
• .data Section: Holds static data.

Common Indicators of Malicious PE Files

• Unusual Entry Points: Suggests tampering.
• Large .rsrc Section: May hide payloads.
• Abnormal Import/Export Tables: Flags suspicious APIs.

Example: Analyzing a PE file to locate its entry point or detect obfuscation.

Reverse Engineering Malware

Reverse engineering decompiles malware to study its logic using tools like IDA Pro, x64dbg, and Ghidra.

• Disassembling: Converts binary to assembly language.
• Debugging: Steps through execution with breakpoints.
• Deobfuscation: Unravels obfuscated or encrypted code (e.g., decrypting an XOR-encoded payload).

Example: Using x64dbg to trace a keylogging malware’s behavior.

Advanced Malware Behavior

Persistence Mechanisms

• Registry Manipulation: Adds auto-run entries for persistence.
• Service Creation: Registers malware as a system service.
• Startup Folder Shortcuts: Places shortcuts for automatic launch.

Example: Malware creating a service that runs on every startup.

Network-Based Behavior

• C2 Communication: Connects to remote servers for instructions.
• DNS Tunneling: Hides traffic in DNS requests.

Example: Analyzing HTTP/HTTPS traffic to a C2 server.

YARA Rules for Malware Detection

YARA identifies malware via pattern matching. Here’s a basic rule:

rule RansomwareDetection {
    strings:
        $s1 = "encrypt"
        $s2 = "AES"
    condition:
        $s1 and $s2
}
      

Advanced techniques include scanning PE modules, ELF files, or memory for fileless malware.

Building Your Own Malware Lab

Set up a secure lab with virtual machines and isolation:

• VirtualBox, VMware, or Cuckoo Sandbox for sandboxing.
• REMnux for specialized analysis.

Best Practices

• Use an air-gapped network to prevent external infections.
• Take VM snapshots before running malware.
• Never run malware on a host system—safety first!

Legal Note: Be aware of laws regarding malware analysis and distribution.

Case Study: Analyzing Real-World Malware

Let’s explore analyzing Zeus or Emotet:

• Static Analysis: Extract strings and review PE structure.
• Dynamic Analysis: Monitor behavior in a sandbox.
• Reverse Engineering: Disassemble to uncover its logic.

Windows APIs Commonly Abused for Malicious Purposes

Process Injection APIs

• CreateRemoteThread: Creates a thread in a remote process for injection.
• VirtualAllocEx: Allocates memory in another process.
• WriteProcessMemory: Writes malicious code into memory.
• NtQueueApcThread: Queues an APC for stealthy injection.

HANDLE hThread = CreateRemoteThread(hProcess, NULL, 0, (LPTHREAD_START_ROUTINE)pFunction, pArg, 0, NULL);
      

Process Manipulation APIs

• OpenProcess: Accesses a process for manipulation.
• TerminateProcess: Terminates security tools.
• SuspendThread/ResumeThread: Pauses or resumes threads.

Persistence Mechanism APIs

• RegSetValueEx: Adds registry entries for startup.
• CreateService/StartService: Runs as a persistent service.
• SetWindowsHookEx: Hooks events (e.g., for keyloggers).
• ShellExecute: Launches payloads.

File and Directory Manipulation APIs

• CreateFile/WriteFile/ReadFile: Manages files for payloads or data theft.
• DeleteFile: Erases evidence.
• SetFileAttributes: Hides files.

Network Communication APIs

• WSAStartup/socket/connect: Sets up network sockets.
• InternetOpen/InternetOpenUrl: Handles HTTP/FTP communication.
• FtpPutFile: Uploads stolen data.

Memory Manipulation APIs

• VirtualAlloc/VirtualFree: Manages memory for payloads.
• RtlCopyMemory: Copies shellcode.
• VirtualProtectEx: Changes memory permissions.

Obfuscation and Anti-Debugging APIs

• CheckRemoteDebuggerPresent/IsDebuggerPresent: Detects debuggers.
• NtSetInformationThread: Hides threads from debuggers.
• Sleep: Delays execution to thwart analysis.

Credential Stealing APIs

• CredEnumerate/CredRead: Extracts credentials from Windows.
• LsaRetrievePrivateData: Steals LSA-stored passwords.

Resources for Malware Analysis

Deepen your knowledge with these:

• Books: Practical Malware Analysis by Sikorski & Honig; Windows Internals by Yosifovich et al.
• Windows API Docs: MSDN.
• PE Format: PE File Format.
• Tools: OllyDbg, Yara, Cuckoo Sandbox.

Stay tuned—more on dynamic/static analysis to come (8-10 tomorrow)!