I have received a few questions on tool recommendations for the CTF. I will list some suggestions below—with a focus on free, open-source, or low-cost tools where available.
The below list covers the challenges we have released so far. I will keep adding tools if needed as we post new challenges.
I strongly recommend using a capable text editor. My favorite is UltraEdit. Other good options are Sublime Text or Atom, possibly with some MIME syntax highlighters.
I recommend using CyberChef for date and format conversions.
When working with MSGs and PSTs, you can use MFCMAPI or OutlookSpy with Outlook.
General Metadata Extraction
You will likely need a general-purpose tool that can extract embedded files, file metadata, etc. Good candidates are X-Ways, Autopsy, or perhaps ExifTool or MetaDiver when you don’t feel like pulling out the big guns.
PDF Deep Dive
When you encounter PDFs, you will likely need a deep dive tool to look into them in detail. You can use PDF CanOpener (with Acrobat), PDF Stream Dumper, pdf-parser.py, etc.