How To Edit Binary Data Using HEX Editors In Linux

Introduction to Hex Editors in Linux

Hex editors are specialized software tools designed to view and edit the raw data of files, disks, and memory. Instead of representing data as Text, these editors display hexadecimal (base 16) content. In Linux environments, hex editors are vital for developers, system administrators, and forensic analysts who must inspect or modify low-level binary data.

The name “hex editor” comes from its core functionality: it operates on binary data but shows each byte in a more readable hexadecimal notation. Text editors manage characters and strings at a higher level but often hide a file’s byte structure. A hex editor reveals exactly what’s stored at each byte offset, which helps in various tasks such as debugging, patching, and analyzing complex binary files.

Whether you are a seasoned developer or a curious enthusiast, understanding how to utilize a hex editor in Linux can significantly enhance your troubleshooting capabilities. These tools allow you to look under the surface of Text layers and examine hidden metadata, file headers, and more. This knowledge lets you directly manipulate bits in executable binaries, network packets, or disk partitions.

This guide provides a comprehensive overview of hex editing in Linux. By the end, you will be equipped with practical techniques, best practices, and a deeper understanding of the hex editor function. From basic navigation to advanced topics like forensic analysis and reverse engineering, the following sections will prepare you to explore and modify binary data confidently.

Why Hex Editors Are Important

Hex editors play a unique role in the Linux toolkit by allowing direct interaction with raw data. Unlike standard Text editors that depend on higher-level representations, hex editors reveal every byte precisely as it exists.

Debugging and Troubleshooting

When programs behave unexpectedly, examining the raw bytes generated by the software can provide clues about memory corruption or data format issues. This level of detail is often overlooked in typical debugging processes.

Patching Files and Binaries

Sometimes, fixing a bug or enabling a hidden feature requires changing a single byte in a compiled binary. Hex editors allow precise alterations without the need for recompilation.

Security and Vulnerability Analysis

Security researchers inspect malicious software and network packets at the byte level to spot embedded strings, encoded payloads, or unusual byte patterns.

Digital Forensics

Forensic experts rely on hex editors to inspect file headers, metadata, and disk artifacts. They can uncover hidden data or reconstruct user actions by pinpointing small details in the binary structure.

Customization and Reverse Engineering

Some applications store configuration data in binary format. Accessing and modifying these files opens up customization opportunities that are otherwise inaccessible.

Hex editors prove their worth in various scenarios by enabling granular control over the bytes composing any data or file. Mastering these tools can streamline troubleshooting and offer insights into the intricate workings of Linux systems.

Popular Hex Editors for Linux

Linux offers numerous hex editors, each with distinct features and interfaces:

xxd

• A command-line utility bundled with Vim. It’s straightforward for quick hex dumps or minor edits.

Bless

• A GUI-based hex editor known for its modern interface and essential hex editing capabilities such as search, replace, and multiple undo levels.

HexEdit / Hexeditor

• Text-based tools offer interactive terminal navigation. They suit those who prefer a TUI (Text-based User Interface) similar to Nano.

bvi (Binary VI)

• Integrates vi-like keybindings, letting users proficient with Vim commands edit binary data rapidly.

GHex

• A polished GUI tool for GNOME environments, offering a simple yet robust feature set for hex editing.

Hexcurse

• Another curses-based hex editor with a command-line interface that supports search, replace, and straightforward file manipulation.

Choose a hex editor based on your workflow needs. Command-line tools like xxd or hexedit are excellent for quick tasks, while GUI tools like Bless or GHex can be more comfortable for in-depth visual analysis.

How to Install Hex Editors on Linux Systems

Installation is generally straightforward, thanks to well-maintained repositories in most Linux distributions. Below are some typical approaches:

Debian/Ubuntu-Based Systems

• xxd

Usually pre-installed with Vim. If missing, install Vim:

sudo apt-get update
sudo apt-get install vim

• Bless

sudo apt-get update
sudo apt-get install bless

• HexEdit

sudo apt-get update
sudo apt-get install hexedit

• bvi

sudo apt-get update
sudo apt-get install bvi

Fedora/CentOS/RHEL

xxd (part of Vim)

sudo dnf install vim

(Use yum instead of dnf on CentOS/RHEL if needed.)

Bless

sudo dnf install bless

HexEdit

sudo dnf install hexedit

bvi

sudo dnf install bvi

Arch Linux/Manjaro

xxd (part of Vim)

sudo pacman -S vim

Bless

sudo pacman -S bless

HexEdit

sudo pacman -S hexedit

bvi

sudo pacman -S bvi

Consider compiling from source if you need the latest version or a specific feature. For detailed instructions on building the tool you prefer, refer to the official documentation or GitHub repositories.

Understanding Hexadecimal Representation

Hexadecimal (base 16) is central to hex editing. Computers store data as bits (0s and 1s), and bytes (eight bits each) are typically shown in hex because they are more compact and readable.

Hexadecimal Digits

• 0 through 9 and A through F, each digit representing 4 bits.
• For example, the binary 1010 is A in hex, and 1111 is F.

One Byte = Two Hex Digits

• A single byte ranges from 0 to 255 in decimal or 00 to FF in hex.
• The ASCII character ‘A’ is 0x41 in hex, while 255 in decimal is 0xFF in hex.

Knowing how bytes map to hex helps identify character encodings and file signatures. For instance, PNG files start with 89 50 4E 47 (i.e., 0x89504E47), which reads as .PNG in ASCII. Familiarity with endianness (byte order) also plays a role, especially in forensics or reverse engineering, where data might be stored in little-endian or big-endian formats.

Getting Started Navigating Data in a Hex Editor

After installation, your first step is learning to navigate through a file’s bytes. Most hex editors use a layout with three main parts:

• Offset Column: This shows the position of the first byte on each line, often in hex.
• Hexadecimal Data Columns: Display the file’s bytes in hex, typically grouped in rows of 8 or 16 bytes.
• The ASCII/Text Column shows the ASCII representation of the bytes if they are printable. Non-printable bytes often appear as dots or blank spaces.

Keyboard Navigation

• Arrow Keys: Move the cursor byte by byte or row by row.
• Page Up / Page Down: Scroll through more significant file chunks.
• Home / End: Jump to the beginning or end of a line or, in some editors, the entire file.

Mouse Support (GUI Editors)

• Click and Drag
• Select bytes to edit or copy.
• Scroll Bars
• Quickly move through large files.

Command-Line Navigation

If you’re using xxd, you may not have an interactive interface. Instead, you can pipe xxd’s output into a viewer:

xxd file.bin | less

This allows scrolling and searching within the terminal using less. Understanding navigation ensures you can locate specific bytes quickly, a crucial skill when modifying data.

Editing Binary Files with a Hex Editor

Editing binary files at the byte level is precise yet risky. A slight mistake can render a file unusable. Follow these guidelines to minimize errors:

• Back-Up the Original File: Always keep a copy before making changes, especially for essential system files or executables.
• Open the File with Appropriate Permissions: If it’s a system file, you might need sudo privileges.
• Locate the Target Bytes: Use known offsets, file signatures, or search features to find where changes are needed.
• Check Endianness: If modifying multi-byte values, know whether they’re stored in little-endian or big-endian format.
• Apply Changes Sparingly: Overwrite only the necessary bytes. Adding or removing bytes can shift offsets and break references elsewhere in the file.
• Save and Verify: Save edits, then test the file in its intended application or environment. If something goes wrong, revert to your backup.

Hex editors are invaluable for simple single-byte tweaks. Consider specialized patching or disassembly tools for complex alterations to avoid accidental corruption.

Searching and Replacing Data in Hex Editors

A robust search-and-replace feature is essential to locate and modify data patterns efficiently. Most hex editors let you search in both hex and ASCII forms:

• Hex Search: Specify a byte pattern (e.g., DE AD BE EF) to find exact matches.
• ASCII/Text Search: Look for readable strings (e.g., “password” or “username”).
• Wildcard Search: Some editors support wildcards for partial matches. This helps when only specific bytes are known or if you’re looking for repeating patterns.

Replacing Data

• Single Replacement: Overwrite specific bytes with new values, often for toggling bits or small-scale edits.
• Batch Replacement: Replace all occurrences of a pattern at once. Use caution; unintended replacements can easily corrupt data.

Large File Considerations

• Incremental Search: Some editors allow incremental searching, scanning large files more effectively.
• External Tools: You can combine xxd with grep, sed, or other command-line utilities to locate patterns in massive files, although you’ll need to map search results back to actual offsets.

Proficiency in search and replace can significantly speed up your workflow, particularly for repetitive editing tasks or pattern-based modifications.

Common Use Cases for Hex Editing in Linux

Hex editors serve as a Swiss Army knife in the Linux environment:

• File Header Inspection and Repair: Fix corrupted headers, verify magic numbers, or ensure file integrity.
• Executable Patch Creation: Toggle instructions or resource references in compiled binaries without recompiling.
• Text String Localization: You can localize applications by replacing static Text strings in binaries, provided you respect string length limits.
• Network Packet Analysis: Analyze raw packets to identify protocol anomalies or embedded malicious data.
• Recovering Deleted Data: Scrutinize unallocated disk space for file fragments that can be pieced together manually.
• Firmware Modifications: Adjust features in device firmware when you know the relevant memory layout.

These varied use cases illustrate the versatility of hex editors. When you need direct, low-level access to data, hex editors are often the most efficient choice.

Forensic Analysis Using Hex Editors

Hex editors are integral to digital forensics. While tools like Autopsy or The Sleuth Kit offer high-level functionalities, hex editors let investigators dig into raw bytes:

• File Signature Validation: Determine if a file’s type has been disguised by looking for its magic number.
• Carving Unallocated Space: Search unallocated disk areas for partial file signatures to recover deleted data.
• Locating Hidden Data: Spot appended or embedded data in legitimate-looking files is a common tactic attackers use.
• Timestamp and Metadata Examination: Interpreting binary-formatted time and attribute data stored by the file system is crucial for building timelines of user actions.

Forensic investigations demand meticulous attention to detail. Hex editors help specialists uncover hidden evidence and accurately document their findings by providing exact byte-level views.

Reverse Engineering and Malware Analysis

Reverse engineering dissects software to understand its internals or identify vulnerabilities, while malware analysis focuses on malicious code. Hex editors are foundational in both:

• Inspecting Strings and Resources: Look for indicators like domain names, IP addresses, or suspicious Text embedded in the binary.
• Identifying Packed/Obfuscated Sections: Locate compressed or encrypted code segments through irregular or repetitive hex patterns.
• Modifying Instructions: Change machine code bytes to disable checks or bypass anti-analysis routines.
• Creating Patches: Neutralize destructive components or remove time checks by editing specific bytes.

Because reverse engineering frequently deals with unknown or poorly documented file structures, hex editors’ flexibility and granularity make them indispensable. Coupled with disassemblers and debuggers, these tools reveal an application’s hidden layers of functionality.

In-Depth Look at xxd

xxd is a command-line tool often included with Vim on Linux systems. It excels at creating hex dumps and converting them back into binary.

Key Features

• Hex Dump Creation: Running xxd filename produces a formatted hex dump, including offsets and ASCII columns.
• Reverse Operation: Use xxd -r to convert a modified hex dump to binary, enabling basic patch workflows.
• Line Length Control: The -c option adjusts the number of bytes per output line (e.g., -c 16 for 16 bytes per line).
• Skipping Bytes: Options like -s (start offset) and -l (length) let you focus on specific file segments.

Limitations

• Lack of Interactivity: No direct navigation or editing within xxd. You usually edit the dumped Text in an external editor, then convert it back.

xxd is perfect for quick insights or scripting scenarios, but a dedicated hex editor with an interactive interface may be more suitable for more complex edits requiring immediate feedback.

Step-by-Step Tutorial: Editing a File with xxd

Below is a simple demonstration of using xxd to modify a small binary file:

Create a Hex Dump

Suppose you have a binary file named sample.bin. Generate its hex dump:

xxd sample.bin > sample.hex

Open the Hex Dump in a Text Editor

Use any Text editor (e.g., Vim, Nano) to open the sample.hex:

vim sample.hex

You’ll see lines with offsets, hex data, and ASCII representation, such as:

00000000: 48 65 6c 6c 6f 2c 20 57  6f 72 6c 64 21  Hello, World!

Modify the Hex Values

Change the bytes you wish to edit. For instance, replace 48 65 6c 6c 6f (“Hello”) with 48 69 2c 20 55 (“Hi, U”). Keep spacing and formatting intact.

00000000: 48 69 2c 20 55 2c 20 57  6f 72 6c 64 21

Convert Back to Binary

After saving the sample.hex, run:

xxd -r sample.hex sample_modified.bin

Verify the Changes

Use xxd again to confirm:

xxd sample_modified.bin | head -n 1

The edit succeeded if the first line has your new byte sequence when you execute the above command on your terminal. Creating a dump, editing it, and reconstructing it is very useful for script runs or any command run where repeated execution is expected.

In-Depth Look at Bless

Bless is a GUI-based hex editor popular in GNOME-based systems. While user-friendly, it also provides advanced features suited for detailed binary inspection.

Core Features

• Tabbed Interface: Open multiple files simultaneously in different tabs.
• Undo/Redo Support: Allows multiple levels of undo, reducing the risk of irreversible mistakes.
• Search and Replace: Locates bytes in both ASCII and hex formats.
• Bookmarks: Mark necessary offsets and return to them quickly.
• Highlighting: Displays search matches and changed bytes in real-time for easier tracking.

Advantages of a GUI

• Visual Clarity: Well-organized data with apparent offset, hex, and ASCII columns.
• Easy Navigation: Scrollbars and familiar menu options are available for those new to hex editing.
• User-Friendly Editing: Instead of memorizing command-line flags or keystrokes, you can leverage menus and dialog boxes.

Potential Drawbacks

• Resource Usage: GUI tools consume more memory and CPU, which is a concern for enormous files.
• Less Scriptability: Automating tasks is simpler with command-line tools than with a GUI-driven interface.

Bless provides a good middle ground for those who prefer graphical interfaces but still need robust hex editing capabilities.

Step-by-Step Tutorial Editing a File with Bless

Here is how to make a simple modification to a binary file using Bless:

Launch Bless

• Open your application menu and search for “Bless.”
• Start Bless to see a clean interface with empty tabs.

Open the Target File

• Click “File” → “Open.”
• Select the binary file (e.g., sample.bin).
• Bless displays the file’s bytes in a grid, showing offsets on the left, hex columns in the middle, and ASCII on the right.

Locate the Bytes to Edit

• Scroll to the area of interest or use “Edit” → “Find” if you know the target string or byte pattern.
• Click on the specific byte you want to modify. It will be highlighted.

Perform the Edit

• Click in the Hex area and type your new byte value (e.g., change 65 to 69 to alter ASCII’ e’ to ‘i’).
• The ASCII panel updates automatically as you edit the hex values.

Save Your Changes

• Go to “File” → “Save” (or use Ctrl + S).
• Select “Save As” and choose a new name to avoid overwriting the original file.

Verify the Result

• Close and reopen the file in Bless or dump it with xxd to confirm your changes.

Bless makes hex editing more accessible, especially for novices. Its graphical approach and straightforward options reduce the learning curve while providing powerful editing capabilities.

Working with Large Files in Hex Editors

Handling huge files can be tricky. Many hex editors load the whole file into memory, which may cause performance slowdowns or potential crashes.

• Partial Loading: Some hex editors can only load the viewable portions. This reduces memory usage by reading data as needed.
• Command-Line Tools: Tools like xxd or od can process files incrementally using flags to specify byte ranges or skip offsets.
• Splitting Files: Use the split command to divide giant files into smaller chunks, then edit each chunk separately before merging.
• Hardware Considerations: Editing large files is more efficient on a 64-bit system with ample RAM.
• GUI vs. Command-Line: GUI editors may struggle with massive data. Command-line approaches often remain more stable and faster under high file-size demands.

Plan carefully when working with multi-gigabyte or terabyte-scale binaries. Select specialized software to work with large files and use the top-down approach to edit data in order not to experience crashes and data loss.

Efficiency Tips and Tricks for Hex Editing

Hex editing can be time-intensive without a streamlined approach. Adopt these techniques to boost efficiency:

• Learn Keyboard Shortcuts: Invest time mastering hotkeys for frequent actions like searching or saving, whether command-line or GUI.
• Use Bookmarks or Markers: Tag offsets to avoid scrolling back and forth in large files.
• Batch Operations: Combine xxd, grep, sed, or other shell commands for repetitive byte pattern replacements.
• Leverage Regular Expressions: If your hex editor supports regex searching, it can help find partial matches or repeating patterns.
• Compare Files: Many hex editors or external diff tools let you compare two binaries, highlighting only the differing bytes.
• Document Your Steps: Track every offset and change, especially when editing critical files or collaborating with others.

Following these tips makes hex editing more efficient, reducing the risk of mistakes and helping you maintain clarity throughout complex modifications.

Scripting and Automation with Hex Editors

While GUI-based editors work well for manual edits, command-line tools are ideal for automating hex editing in larger workflows:

• Combining xxd with Shell Commands

Create a hex dump, use sed or awk to replace patterns, then convert the dump back to binary:

xxd input.bin | sed 's/DE AD BE EF/BA AD F0 0D/g' | xxd -r > output.bin

• Python or Perl Scripts
• Read and write binary data with fine-grained control. Useful for dynamic patching and checksum calculations.
• Automated Validation
• In CI/CD pipelines, automatically verify hashes before and after editing to ensure only intended bytes are changed.

Automation reduces manual effort and minimizes human error. Once you establish reliable scripts, repetitive hex editing tasks become quick and reproducible.

Permissions and Security Considerations

Hex editing can pose risks if done irresponsibly. Manipulating critical files or executables requires care:

• Principle of Least Privilege: Edit files only if you have the necessary permissions. For system files, use sudo minimally and always verify changes.
• Validate File Integrity: Use checksums or digital signatures to confirm that only intended bytes were altered.
• Legal and Ethical Boundaries: Be mindful of laws and organizational policies. Reverse engineering, DRM tampering, or malware modification can have legal implications.
• Backups and Logs: Always keep an unaltered version of the file and log every change you make, including offsets and original values.
• Secure Environment: Perform sensitive edits on trusted systems. Avoid unverified machines where data interception could occur.

Operating with caution guarantees that the system will run steady and won’t be accidentally destroyed or put into legal jeopardy. Hex editing is a very powerful tool, and hence, it has to be used like any powerful tool on the market.

Troubleshooting Common Hex Editor Issues

Even experienced users encounter roadblocks. Here are frequent challenges and possible remedies:

• File Not Opening: Too large for the editor’s buffer. Try partial loading or a command-line tool.
• Corrupted Output: A single wrong byte can break a file. Use undo features or maintain backups to recover quickly.
• Permissions Denied: Ensure you have write access. Copy system files to a writable directory before editing, then replace them with sudo if needed.
• Non-ASCII Characters: Hex editors display unprintable characters as dots or blanks. This is normal unless you suspect the data should be readable Text.
• Performance Lag: Close resource-intensive applications, disable editor features like auto-highlighting, or switch to a lighter tool.

Most hex editor problems can be resolved by systematic troubleshooting and awareness of file sizes, memory limits, and proper permissions.

Best Practices for Hex Editing in Linux

Keep these principles in mind for smooth, risk-free editing:

• Plan Your Changes: Understand the target file format and decide which bytes to modify before starting.
• Consider Version Control: Git or other systems can track changes, although they’re not ideal for large binaries.
• Document Everything: Note every offset, original byte, and new byte, which is especially helpful for collaborative or forensic work.
• Test Often: If you modify an executable, test it in a safe environment to confirm functionality.
• Maintain Multiple Backups: Keep multiple copies to revert if something breaks.
• Master Your Editor: Explore advanced features and shortcuts to improve your workflow.
• Stay Updated: Bug fixes or new functionalities in hex editors can make your life easier and safer.

Adhering to these best practices minimizes errors, preserves data integrity, and helps you get the most out of any hex editor you choose.

Additional Tools and Resources

Beyond traditional hex editors, other utilities can enhance your binary editing and analysis:

• Binwalk: I specialize in detecting embedded files and code in firmware or larger binaries.
• Radare2: An open-source reverse engineering framework with disassembly, debugging, and hex editing.
• Foremost/Scalpel: Useful for file carving in forensic contexts by searching for file headers and footers.
• Ghidra: The NSA developed a powerful reverse engineering suite featuring disassembly, decompilation, and basic hex editing capabilities.
• Online Hex Editors: It is handy for small files or quick edits when you can’t install software locally.
  
• Documentation and Community Forums: The Linux Documentation Project, specialized GitHub repos, and Reverse Engineering Stack Exchange forums offer tutorials, discussions, and guidance.

Combine these tools with your preferred hex editor for a more robust approach to binary analysis and modifications.

Conclusion

Judging by the importance of hex editors with Linux users, I won’t go a day without having a hex editor at my disposal. They allow us to analyze the raw data stored in files, executables, memory dumps, etc., giving no other tools the same opportunity when you need to make a minor modification or rework a program through forensic analysis or reverse code engineering(hex editing empowers the chapter owned of binary data than any other tool can offer).

This guide covered:

• Fundamental concepts of hex editors and their importance for low-level operations
• Popular editors and installation methods on various distributions
• Basic to advanced usage: searching, replacing, patching files, and handling extensive data
• Specialized applications, such as forensics and malware analysis, illustrate how powerful hex editors can be
• Key security considerations and best practices to guarantee data integrity and compliance

As an extension of such hex editing, insight is gained on a deeper level of a particular system. In other cases, you may be fixing a program with a hex editor, detecting hidden data, or reversing a sketchy program – a hex editor is a tool that gives you much-needed visibility and control. Use these tools cautiously as a first step to save a copy of critical data and work ethically. The time and exercise will make you fearless in addressing high-level data analysis challenges to convert mere bytes into helpful information.

About the writer

Vinayak Baranwal wrote this article. Use the provided link to connect with Vinayak on LinkedIn for more insightful content or collaboration opportunities.