Welcome back, aspiring forensic investigators!

Today, we continue our exploration of digital forensics with a hands-on case study. So far, we have laid the groundwork for understanding forensic principles, but now it’s time to put theory into practice. Today we will analyze a malicious USB drive, a common vector for delivering payloads, and walk through how forensic analysts dissect its components to uncover potential threats.

USB drives remain a popular attack vector because they exploit human curiosity and trust. Often, the most challenging stage of the cyber kill chain is delivering the payload to the target. Many users are cautious about downloading unknown files from the internet, but physical media like USB drives can bypass that hesitation. Who wouldn’t be happy with a free USB? As illustrated in Mr. Robot, an attacker may drop USB drives in a public place, hoping someone curious will pick them up and plug them in. Once connected, the payload can execute automatically or rely on the victim opening a document. While this is a simple strategy, curiosity remains a powerful motivator, which hackers exploit consistently. 

(Read more: https://hackers-arise.com/mr-robot-hacks-how-elliot-hacked-the-prison/)

Forensic investigation of such incidents is important. When a USB drive is plugged into a system, changes may happen immediately, sometimes leaving traces that are difficult to detect or revert. Understanding the exact mechanics of these changes helps us reconstruct events, assess damage, and develop mitigation strategies. Today, we’ll see how an autorun-enabled USB and a malicious PDF can compromise a system, and how analysts dissect such threats.

Analyzing USB Files

Our investigation begins by extracting the files from the USB drive. While there are multiple methods for acquiring data from a device in digital forensics, this case uses a straightforward approach for demonstration purposes.

After extraction, we identify two key files: a PDF document and an autorun configuration file. Let’s learn something about each.

Autorun

The autorun file represents a legacy technique, often used as a fallback mechanism for older systems. Windows versions prior to Windows 7 frequently executed instructions embedded in autorun files automatically. In this case, the file defines which document to open and even sets an icon to make the file appear legitimate.

On modern Windows systems, autorun functionality is disabled by default, but the attacker likely counted on human curiosity to ensure the document would still be opened. Although outdated, this method remains effective in environments where older systems persist, which are common in government and corporate networks with strict financial or operational constraints. Even today, autorun files can serve as a backup plan to increase the likelihood of infection.

PDF Analysis

Next, we analyze the PDF. Before opening the file, it is important to verify that it is indeed a PDF and not a disguised executable. Magic bytes, which are unique identifiers at the beginning of a file, help us confirm its type. Although these bytes can be manipulated, altering them may break the functionality of the file. This technique is often seen in webshell uploads, where attackers attempt to bypass file type filters.

To inspect the magic bytes:

bash$ > xxd README.pdf | head

In this case, the file is a valid PDF. Opening it appears benign initially, allowing us to read its contents without immediate suspicion. However, a forensic investigation cannot stop at surface-level observation. We will proceed with checking the MD5 hash of it against malware databases:

bash$ > md5sum README.pdf

VirusTotal and similar services confirm the file contains malware. At this stage, a non-specialist might consider the investigation complete, but forensic analysts need a deeper understanding of the file’s behavior once executed.

Dynamic Behavior Analysis

Forensic laboratories provide tools to safely observe malware behavior. Platforms like AnyRun allow analysts to simulate the malware execution and capture detailed reports, including screenshots, spawned processes, and network activity.

Key observations in this case include multiple instances of msiexec.exe. While this could indicate an Adobe Acrobat update or repair routine, we need to analyze this more thoroughly. Malicious PDFs often exploit vulnerabilities in Acrobat to execute additional code.

Next we go to AnyRun and get the behavior graph. We can see child processes such as rdrcef.exe spawned immediately upon opening.

Hybrid Analysis reveals that the PDF contains an embedded JavaScript stream utilizing this.exportDataObject(...). This function allows the document to silently extract and save embedded files. The file also defines a /Launch action referencing Windows command execution and system paths, including cmd /C and environment variables such as %HOMEDRIVE%%HOMEPATH%.

The script attempts to navigate into multiple user directories in both English and Spanish, such as Desktop, My Documents, Documents, Escritorio, Mis Documentos, before executing the payload README.pdf. Such malware could be designed to operate across North and South American systems. At this stage the malware acts as a dropper duplicating itself.

Summary

In our case study we demonstrated how effective USB drives can be to deliver malware. Despite modern mitigations such as disabled autorun functionality, human behavior, especially curiosity and greed remain a key vulnerability.  Attackers adapt by combining old strategies with new mechanisms such as embedded JavaScript and environment-specific paths. Dynamic behavior analysis, supported by platforms like AnyRun, allows us to visualize these threats in action and understand their system-level impact. 

To stay safe, be careful with unknown USB drives and view unfamiliar PDF files in a browser or in the cloud with JavaScript blocked in settings. Dynamic behavior analysis from platforms like AnyRun, VirusTotal and Hybrid Analysis helps us to visualize these threats in action and understand their system-level impact.

If you need forensic assistance, we offer professional services to help investigate and mitigate incidents. Additionally, we provide classes on digital forensics for those looking to expand their skills and understanding in this field.

The post Digital Forensics: Analyzing a USB Flash Drive for Malicious Content first appeared on Hackers Arise.

Welcome, aspiring forensic investigators!

Welcome to the new Digital Forensics module. In this guide we introduce digital forensics, outline the main phases of a forensic investigation, and survey a large set of tools you’ll commonly meet. Think of this as a practical map: the article briefly covers the process and analysis stages and points to tools you can use depending on your objectives. Later in the course we’ll dig deeper into Windows and Linux artifacts and show how to apply the most common tools to real cases.

Digital forensics is growing fast because cyber incidents are happening every day. Budget limits, legacy systems, and weak segmentation leave many organizations exposed. AI and automation make attacks easier and fasterю. Human mistakes, especially successful phishing, remain a top cause of breaches. When prevention fails, digital forensics helps answer what happened, how it happened, and what to do next. It’s a mix of technical skills, careful procedure, and clear reporting.

What is Digital Forensics?

Digital forensics (also called computer forensics or cyber forensics) is the discipline of collecting, preserving, analyzing, and presenting digital evidence from computers, servers, mobile devices, networks, and storage media. It grew from early law-enforcement needs in the 1980s into a mature field in the 1990s and beyond, as cybercrime increased and investigators developed repeatable methods.

Digital forensics supports incident response, fraud investigations, data recovery, and threat hunting. The goals are to reconstruct timelines, identify malicious activity, measure impact, and produce evidence suitable for legal, regulatory, or incident-response use.

Main Fields Inside Digital Forensics

Digital forensics branches into several focused areas. Each requires different tools and approaches.

Computer forensics

Focuses on artifacts from a single machine: RAM, disk images, the Windows registry, system logs, file metadata, deleted files, and local application data. The aim is to recreate what a user or a piece of malware did on that host.

Network forensics

Covers packet captures, flow records, and logs from routers, firewalls and proxies. Analysts use network data to trace communications, find command-and-control channels, spot data exfiltration, and follow attacker movement across infrastructure.

Forensic data analysis

Deals with parsing and interpreting files, database contents, and binary data left after an intrusion. It includes reverse engineering malware fragments, reconstructing corrupted files, and extracting meaningful information from raw or partially damaged data.

Mobile device forensics

Targets smartphones and tablets. Android and iOS store data differently from desktops, so investigators use specialized methods to extract messages, app data, calling records, and geolocation artifacts.

Hardware forensics

The most specialized area: low-level analysis of firmware, microcontrollers, and embedded devices. This work may involve extracting firmware from chips, analyzing device internals, or studying custom hardware behavior (for example, the firmware of an IoT transmitter or a skimmer installed on an ATM).

Methods and approaches

Digital forensics work generally falls into two modes: static (offline) analysis and live (in-place) analysis. Both are valid. The choice depends on goals and constraints.

Static analysis

The traditional workflow. Investigators take the device offline, build a bit-for-bit forensic image, and analyze copies in a lab. Static analysis is ideal for deep disk work: carving deleted files, examining file system metadata, and creating a defensible chain of custody for evidence.

Live analysis

Used when volatile data matters or when the system cannot be taken offline. Live techniques capture RAM contents, running processes, open network connections, and credentials kept in memory. Live collection gives access to transient artifacts that vanish on reboot, but it requires careful documentation to avoid altering evidence.

Live vs Static

Static work preserves the exact state of disk data and is easier to reproduce. Live work captures volatile evidence that static imaging cannot. Modern incidents often need both. They start with live capture to preserve RAM and active state, then create static images for deeper analysis.

The forensic process

1. Create a forensic image

Make a bit-for-bit copy of storage or memory. Work on the copy. Never change the original.

2. Document the system’s state

Record running processes, network connections, logged-in users, system time, and any other volatile details before power-down.

3. Identify and preserve evidence

Locate files, logs, configurations, memory dumps, and external devices. Preserve them with hashes and a clear chain of custody.

4. Analyze the evidence

Use appropriate tools to inspect logs, binaries, file systems, and memory. Look for malware artifacts, unauthorized accounts, and modified system components.

5. Timeline analysis

Correlate timestamps across artifacts to reconstruct the sequence of events and show how an incident unfolded.

6. Identify indicators of compromise (IOCs)

Extract file hashes, IP addresses, domains, registry keys, and behavioral signatures that indicate malicious activity.

7. Report and document

Produce a clear, well-documented report describing methods, findings, conclusions, and recommended next steps.

Toolset Overview

Below is a compact reference to common tools grouped by purpose. Later modules will show hands-on use for Windows and Linux artifacts.

Imaging and acquisition

FTK Imager — Windows tool for creating forensic copies and basic preview.

dc3dd / dcfldd — Forensic versions of dd with improved logging and hashing.

Guymager — Fast, reliable imaging with a GUI.

DumpIt / Magnet RAM Capture — Simple, effective RAM capture utilities.

Live RAM Capturer — For memory collection from live systems.

Image mounting and processing

Imagemounter — Mount images for read-only analysis.

Libewf — Support for EnCase Evidence File format.

Xmount — Convert and remap image formats for flexible analysis.

File and binary analysis

HxD / wxHexEditor / Synalyze It! — Hex editors for direct file and binary inspection.

Bstrings — Search binary images with regex for hidden strings.

Bulk_extractor — Extract emails, credit card numbers, and artifacts from disk images.

PhotoRec — File carving and deleted file recovery.

Memory and process analysis

Volatility / Rekall — Industry standard frameworks for memory analysis and artifact extraction.

Memoryze — RAM analysis, including swap and process memory.

KeeFarce — Extracts KeePass data from memory snapshots.

Network and browser forensics

Wireshark — Packet capture and deep protocol analysis.

SiLK — Scalable flow collection and analysis for large networks.

NetworkMiner — Passive network forensics that rebuilds sessions and files.

Hindsight / chrome-url-dumper — Recover browser history and user activity from Chrome artifacts.

Mail and messaging analysis

PST/OST/EDB Viewers — Tools to inspect Exchange and Outlook data files offline.

Mail Viewer — Supports multiple mailstore formats for quick inspection.

Disk and filesystem utilities

The Sleuth Kit / Autopsy — Open-source forensic platform for disk analysis and timeline creation.

Digital Forensics Framework — Modular platform for file and system analysis.

Specialized extraction and searching

FastIR Collector — Collects live forensic artifacts from Windows hosts quickly.

FRED — Registry analysis and parsing.

NTFS USN Journal Parser / RecuperaBit — Recover change history and reconstruct deleted/changed files.

Evidence processing and reporting

EnCase — Commercial suite for imaging, analysis, and court-ready reporting.

Oxygen Forensic Detective — Strong platform for mobile device extraction and cloud artifact analysis.

Practical notes and best practices

a) Preserve original evidence. Always work with verified copies and record cryptographic hashes.

b) Capture volatile data early. RAM and live state can vanish on reboot. Prioritize their collection when necessary.

c) Keep clear records. Document every action, including tools and versions, timestamps, and the chain of custody.

d) Match tools to goals. Use lightweight tools for quick triage and more powerful suites for deep dives.

e) Plan for scalability. Network forensics can generate huge data sets. Prepare storage and filtering strategies ahead of time.

Summary

We introduced digital forensics and laid out the main concepts you’ll need to start practical work: the different forensic disciplines, the distinction between live and static analysis, a concise process checklist, and a broad toolset organized by purpose. Digital forensics sits at the intersection of incident response, threat intelligence, and legal evidence collection. The methods and tools presented here form a foundation. In later lessons we’ll work through hands-on examples for Windows and Linux artifacts, demonstrate key tools in action, and show how to build timelines and extract actionable IOCs. 

Keep in mind that good forensic work is disciplined, repeatable, and well documented. That’s what makes the evidence useful and the investigation reliable.

If you need forensic assistance, we offer professional services to help investigate and mitigate incidents. Additionally, we provide classes on digital forensics for those looking to expand their skills and understanding in this field.

The post Digital Forensics: Getting Started Becoming a Forensics Investigator first appeared on Hackers Arise.