Prompt

The hackers have hidden a message in this image. Find out what it is.

Walk-Through

This challenge involves using the strings Linux command to find a hidden message. A random portion of the image file was modified to insert the message, which is why there is a distortion in the image. The horizontal distortion that occurs near the eye is a result of the corruption caused by inserting the hidden message randomly within the image data.

Background:

Recall from the bases challenge about how data can be converted from one form to another. Some values in binary that are used in files are not convertible to text characters. strings will pull any binary data out of the file that corresponds to a text character. Text characters would include letters (abc), numbers (123), or symbols (&^,*).

Here is the output of the strings command used on the STEG.jpg file:

Guide:

Searching Standard Output (stdout) : grep

The output of the strings command can be searched with another command; grep.

grep is a powerful search command that looks for characters matching the exact string entered by the user. grep is often used with the pipe character ( | ) to search the output of other commands or to format the output of grep.

This challenge specifies that a flag is contained in the image, therefore, grep could be used to look for binary data that converts to characters resembling the standard flag format. This can be done using the command below:

strings STEG1.jpg | grep SKY

Using strings is a quick way to see if a flag is hidden within the file without needing to open other programs. However, this challenge could also be solved using a hex editor and searching for SKY as shown below:

Questions

1. What is the hidden flag in the image?

Run the strings command on the image and search for text that contains “SKY”

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