Hacking Lab 0x03   Using md5sum to Verify Integrity or Find Covert Files
Channel: The Expat Professor
Date: 2022-07-21

Hacking Lab 0x03 - Using md5sum to Verify Integrity or Find Covert Files
© Paul W. Poteete, 2016

Overview:
 This lab introduces the student to md5sum and a potential use in ethical hacking.  Several commands will be used to complete the exercise using Linux and security knowledge.

 As a general note, additional labs often discuss the commands in greater detail.  This method presents the information in a “What” then “Why” model, allowing the students to experiment with the tools before studying the tools in hope that this will generate greater understanding when the tools are studied in the future.

Resources:
 Images.tar.gz (contains original MD5SUM)

Attacker Tools:
 tar
 md5sum
 sdiff
 openstego

Process:
1) Download the Images.tar.gz file

2) Put the file into a "working" directory.  The term "working" is used to represent a location that will allow you to work on the files without disturbing other files.
mkdir Images
cp Images.tar.gz Images/
cd Images

2) untar the file
tar xvzf Images.tar.gz

3) Create an MD5SUM of all of the Wallpaper Images
md5sum *png OUTBRACKET_REMIOVED_BY_YOUTUBE md5sum.NEW

4) Verify the md5sum from the tar with the new md5sum
Note: Discover the file that has a different md5sum by reviewing the output: look for the "|" character.
sdiff  md5sum.txt  md5sum.NEW

5) Use openstego to extract the payload from the file that did not pass the md5sum check.
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