PicoCTF 2018 - Forensics Warmup 2

Information

Points	Category	Level
50	Forensics	Easy

Hmm for some reason I can’t open this PNG? Any ideas?

How do operating systems know what kind of file it is? (It’s not just the ending!

Make sure to submit the flag as picoCTF{XXXXX}

Let’s download the file, we can see it’s extension name is png, but if we try to open the file we got an error:

Fatal error reading PNG image file: Not a PNG file

so if it’s not a PNG file what is it? let’s use a terminal command to check it -

  Open terminal -> move to the folder of the file (by cd) -*> file flag.png

file - command that show us information about the file. the information we get back is:

flag.png: JPEG image data, JFIF standard 1.01, resolution (DPI), density 75x75, segment length 16, baseline, precision 8, 909x190, frames 3

so it’s a JPEG file and not PNG, we want to rename the extension of the file to JPEG go back to the terminal

mv flag.png flag.jpeg

mv - command that move files from path to path and can also be used for rename a file

picoCTF{extensions_are_a_lie}