picoCTF 2019 What Lies Within Writeup

What Lies Within is a forensics puzzle worth 150 points.

The description of this puzzle:

There's something in the building. Can you retrieve the flag?

An image buildings.png is provided, which shows a picture of a building:

buildings.png

First, I tried using exiftool and just looking around at the picture. This is likely a steganography challenge based on it being in the Forensics category and the puzzle being an image. Usually for steganography challenges, I start by simply trying a bunch of known decoders against it.

In this instance, I got a hit with zsteg:

Solved with zsteg.

I should really sit down one day and make a list of decoders and what kinds of files they work on, and script something out to automate these easier challenges.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s