🔮 Challenge 6: The Mystery File
Advanced Forensics: File extensions can be faked, but a file's "magic numbers" never lie!
📖 The Story
The security team found a file called
Every file format has a specific byte sequence at the beginning, called its "magic number" or "file signature." For example, PDF files always start with
Download this mystery file, figure out its true identity, open it the right way — and the flag is yours!
📥 Download Mystery File (mystery_file.dat)
mystery_file.dat on a compromised computer. Its extension says .dat, but experienced forensic analysts know — file extensions can be changed to anything!Every file format has a specific byte sequence at the beginning, called its "magic number" or "file signature." For example, PDF files always start with
%PDF, and PNG images start with 89 50 4E 47.Download this mystery file, figure out its true identity, open it the right way — and the flag is yours!
🛠️ How to Identify a File's True Type
- Open the file in a hex editor and check the first few bytes
- Online tools: search "hex editor online" or "file signature checker"
- Common magic numbers:
%PDF= PDF,PK= ZIP,89 PNG= PNG - Command line:
file mystery_file.dat(Linux/Mac) orxxd mystery_file.dat | head - Easiest method: try renaming
.datto other extensions and see what opens!
💡 Hint 1: How do I check the first bytes?
You can open the .dat file with a text editor (like Notepad) and look at the very beginning for recognizable text. Or use an online hex viewer.
💡 Hint 2: I know the file type — now what?
If the file starts with %PDF, it's actually a PDF file! Rename the extension from .dat to .pdf, then open it with a PDF reader to see the flag.