HackDay - Stegano

In this challenge, we are provided with a .wav file that, at first glance, appears to be a simple audio file. Our task is to analyze the file and uncover a hidden flag.

Step 1: Playing the Audio Link to heading

I started by playing the audio, expecting something unusual—perhaps some hidden message or distortion—but everything sounded normal. There was no apparent clue in the audio playback.

Step 2: Using ffprobe to Analyze Metadata Link to heading

To dig deeper, I used ffprobe, a tool from the FFmpeg suite, to extract metadata and technical details from the .wav file.

What is ffprobe? ffprobe is a powerful command-line utility that provides detailed metadata and insights into the structure of media files.

Good for:

  • Extracting metadata
  • Inspecting streams (audio, video, subtitles)
  • Detecting hidden data
  • Analyzing file formats
  • Identifying hidden attachments

Screenshot

Unfortunately, nothing unusual was found in the metadata.

Step 3: Using exiftool for Further Metadata Analysis Link to heading

Next, I used exiftool to analyze the file further, hoping to uncover hidden data or anomalies.

What is exiftool? exiftool is a command-line tool designed to extract and manipulate metadata from files like images, audio, and videos.

Good for:

  • Extracting metadata
  • Identifying embedded data
  • Analyzing file structures
  • Revealing edits or manipulations
  • Extracting hidden attachments
  • Searching for anomalies

Screenshot

Unfortunately, even exiftool revealed nothing suspicious.

Step 4: Extracting Strings with strings Link to heading

Since metadata analysis didn’t yield results, I moved on to search for hidden information in printable characters using strings.

What is strings? strings is a simple command-line tool that extracts printable ASCII and Unicode characters from binary files.

Good for:

  • Extracting printable characters
  • Searching for keywords (grep-friendly)
  • Revealing hidden data
  • Locating steganographic markers (some tools leave identifiable markers in files)

Output: Screenshot

Despite scanning for keywords and hidden data, there was no luck with strings.

Step 5: Binary Analysis with Binwalk Link to heading

Still empty-handed, I decided to dig deeper into the binary structure using binwalk.

What is binwalk? binwalk is a tool for analyzing binary files to detect and extract:

  • Embedded files (e.g., images, archives)
  • Hidden data
  • Compressed or encrypted sections
  • Steganographic payloads

Command used: binwalk file.wav

However, even binwalk failed to provide any significant clues.

Step 6: Hexadecimal Analysis with xxd Link to heading

Finally, I decided to inspect the file’s raw binary data using xxd.

What is xxd? xxd creates a hexadecimal dump of a file, allowing detailed inspection of binary content.

Good for:

  • Viewing raw data in hex and ASCII formats
  • Searching for patterns or keywords
  • Analyzing file structure at a low level
  • Inspecting steganographic payloads or hidden data

Command used: xxd file.wav

After carefully analyzing the binary data, I finally discovered the flag embedded deep within the file: Screenshot