What is a File Format?

Let's explore what a file format is, and provide a different view on it. We dive into polyglots, file format research and the impact on security.

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[yuxin]

This video is pretty fascinating. With many years of experience using Linux and command line, I am already familiar with the fact that file format is just a trick (every file is just a binary stream anyway), but I am sill surprised that you can easily craft files to be interpreted by multiple programs differently. I am not sure whether it's a good thing or a bad thing. From a developer's perspective, we want the file format to be unambiguous, because we know from experience that ambiguity is a common source of bugs and unexpected behaviors. However, sometimes we also want flexibility and tolerance. For example, we want to add more features to file format but not break the older version program, which means we shouldn't be overly strict on recognizing format. These two design principle are sometimes conflicting to each other, and I think it is the main cause of the issue.

[philipk]

Aah yes! the Schrodinger's zip file.

[Sunpy_Emily]

The scene with dark background, a table and a simple t-shirt makes this feel like an interrogation scene where police is asking the criminal questions.

[johnnygr]

The conversation went like this:
- WTF did you do?
- You dog...
- Zip it man!

[panagiotispetridis]

I really like this type of videos. The explanations where really good the quality is very high and overall I can confidently say that I've learnt something I didn't know before!

[YotaNinja]

I remember my first time learning about this file format trick was probably about 2005-2006 on 4chan of all places. Someone uploaded an image, it was the cover of a C++ textbook, or some C language. I can't quite remember, but what I do remember was you could download the image, and extract that exact document from it. They embedded the textbook within the image itself, and used any image hosting site to discretely share it with people. I was blown away.

[MrKristian]

If anyone has seen this image going around on Discord; "Please don't open me in the browser".

Basically 2 image png animation. Renamed to .zip, gives a .mp3 file inside, containing some metadata about opening the audio in a image viewer.
Pretty cool, took half of the day to get to the end of it.

[shadytv]

I'm someone in the category of people freaking out about closed source binwalk so I see files agnostically already. But I thought - "Hey, If I give this video a chance I'm sure LiveOverFlow will teach me something new" - All I can say is WOW The idea of not encapsulating but "programming" a file into the zip format is a complete paradigm shift. I will never be able to look at files in the same way again holy shit bro you just blew my mind.

[solomioist]

LiveOverflow: „You don’t want to do PDF by hand“

Me: *cries in LaTeX*

[p.]

My mind was absolutely blown away. I've never thought that the same file could be interpreted differently. This is eye-opening for me.

[stevepoper]

I remember being blown away by file extensions when I played DDLC

[BGroothedde]

The 010 tool is pretty awesome, reminds me of something similar I made for terminals - but more advanced and with a hex editor. Thanks for sharing that!

[mikee.]

Love the new style of videos. Also the video quality is absolutely stunning, so well produced!

[hafidhzouahi]

LiveOverFlow: hiding files in files is not fun
justCTF: yes

[attention_shopping]

love the bit about CTF at the end -- that makes so much sense!

[himansh]

This whole channel is a blessing in my Cybersecurity journey! thankyou soo much for creating such level of content...

[Brlitzkreig]

Wow, you make it so easy for people to understand these complex topics!

[otkchk]

LiveOverflow 2016 - finding a parser differential in loading ELF
LIveOverflow 2020 - what is a file format

just joking. top notch stuff I didn't know.

[joshinils]

"grew up with a commandline" yes, you could say that i grew up when i started using linux a few years ago

[gv]

010's template feature is the best one I have seen yet in any hex editor. It's really useful for reversing proprietary file formats.