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Steganography: The art of hiding stuff in stuff so others don't find your stuff (Hacking Illustrated Series InfoSec Tutorial Videos)

Steganography: The art of hiding stuff in stuff so others don't find your stuff

        This is a presentation I was working on for the malware class I"m enrolled in. For some reason my voice was cracking while recording it, but I guess it was good practice for the live version I"ll do tomorrow. Besides just an introduction to Steganography, I"ll also talk a little about my SnarlBot project that will attempt to use stego in a command and control channel.

Slides:
http://www.irongeek.com/downloads/stego.pdf
http://www.irongeek.com/downloads/stego.pptx

 

Right click and download from:

Text from the slides for the sake of links:

Steganography
The art of hiding stuff in stuff so others don"t find your stuff
&
A little about my Botnet Stego C&C project
Some information drawn from following articles:

Exploring Steganography:Seeing the Unseen
http://www.jjtc.com/pub/r2026.pdf
With a little from
Lossy Compression Tolerant Steganography
http://nas.takming.edu.tw/chkao/LNCS2001.pdf
Hide and Seek: An Introduction to Steganography
http://www.citi.umich.edu/u/provos/papers/practical.pdf


Definition
* Steganography is the practice of hiding data in other data in an effort to keep 3rd parties from knowing that the intended message is even there
* Encryption's ugly step brother
* It has art aspects since human judgment is involved
Isn"t this security though obscurity?
* Sort of
* With Encryption alone, 3rd parties may not be able to read the message, but they know one was sent
* In some cases, just being caught sending a message can bring suspicion, or give information to the 3rd party
- Why is this person hiding something?
- Crypto laws http://rechten.uvt.nl/koops/cryptolaw/ 
- Why all the communication right now?
* Resistant to "Rubber-hose Cryptanalysis"
Thanks to Marcus J. Ranum for that lovely term


About the 1st article
* "Exploring Steganography: Seeing the Unseen" was published in 1998
* Over the last 12 years, bandwidth and storage have skyrocketed
* 24bit images are common now, as are PNGs that use lossless compression
* Still, the article gives a good intro to the subject which is why I chose it over some newer articles
* The article mostly talks about images, but Steganography can be used in many other places
 

Historical examples
* Greeks and wax covered tablets
* Histiaeus and the shaved head
* Invisible inks in WWII
* Open coded messages (Pershing example)
* Microdots

Images
* Information about pixels


LSB (Least Significant Bit) Encoding
* Can you tell the difference?
Can you tell the difference?


Why lossy formats/re-encoding are problems
Image resizing/recompressing
* Causes changes in palette and bit order
* May be solvable with redundancy
* Hamming Code
http://en.wikipedia.org/wiki/Hamming_code
http://candle.ctit.utwente.nl/Docs/wp5/tel-sys/exercises/datalinkp2p/hamming74demo.html 
* James Shewmaker
https://media.defcon.org/dc-16/video/Defcon16-James_Shewmaker-StegoFS.m4v 


Digital Watermarks
* Copyright enforcement
* Redundant pattern encoding to resist data loss during resize/re-encoding
* Change the media enough to kill the watermark, the media degrades beyond the point of usefulness (Think leaked movies)


Detection
* Access to the original image
* Statistical analysis
(source material category makes a big difference)
* Odd artifacts


Stego Tools
* Since the article is 12 years old, lets look for newer tools:
* Search Sourceforge
http://sourceforge.net/search/?type_of_search=soft&words=Steganography 
* Steghide (JPEG, BMP, WAV and AU)
http://steghide.sourceforge.net/ 
* Outguess
http://www.outguess.org/ 
* My example code
http://www.irongeek.com/i.php?page=security/unicode-and-lsb-stego-code 
 

Other steganography examples
* Truecrypt hidden volumes
http://www.irongeek.com/i.php?page=videos/truecrypt1
* Office 2007 documents as ZIP archives
Putting a file inside of a DOCX, it?s just a ZIP file with some XML, just add you inserted file name into [Content_Types].xml so the DOCX does not report as corrupted.
Tacked on to image (copy /B image.jpg+putty.zip test.jpg)
Slack space
Alternative Data Streams
More on these:
http://www.irongeek.com/i.php?page=videos/anti-forensics-occult-computing 
* EXIF or other Metadata
* IP over ICMP or DNS
 

Text Based Stego
Pros:
* Most "Web 2.0" apps accept text, not necessarily images
* Text takes up little space
Cons:
* Harder to encode and be stealthy
* Less bits to hide in
* In some ways harder to code from a logic standpoint
 

Pershing Example:
Which Character?
The key is knowing what character to pay attention to:
* Apparently neutral"s protest is thoroughly discounted and ignored. Isman hard hit. Blockade issue affects pretext for embargo on by products, ejecting suets and vegetable oils.
* pershingsailsfromnyjunei
* Pershing sails from NY June 1
 

Unicode Stego
* 65536 positions in UTF16
* Characters that look similar (homoglyphs) are encoded at multiple positions
* Using these, values can be encoded
!"$%&"()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~
* Example:
Code Point 65 = A
Code Point 65315 =A


Antonio Alcorn"s Work
CGI can be found at:
http://www.cs.trincoll.edu/~aalcorn/steganography/encrypt 
* "??llo, ? need s?m? ?ov?? t?xt t? use."
* The word "test" is encoded above


My work on Unicode Stego
http://www.irongeek.com/i.php?page=security/unicode-and-lsb-stego-code 
* The Latin alphabet is encoded more than once in Unicode, high values used to represent 1s, lows represent 0s (most characters I could just recode as full width Latin by adding 65248)
 

Snow:White Space Stego
* http://www.darkside.com.au/snow/
* http://fog.misty.com/perry/ccs/snow/jsnowapp/jsnowapp.html 
Other Ideas I"m working on
How about a code book for leet/texting/misspellings speak?

I can has cheese burger? How are you?
i can haz chee$e burg3r? How are you? = 01000001 = A
i can has ch3ese burger? H0w r you? = 01011010 = Z
Red are encoded
Blue characters are ones that could have been encoded, but were not needed
Issues:
* Encoder and decoder will be tougher program, but I could do it all in low ASCII.
* I would likely have less room to add data.
More ideas/concepts I"ve been playing with
* Simplify the language to conserve space

* Give the user a set of control characters they have to integrate into their writing (Punctuation)
- "test" becomes ",&:!,",&"
- User adds word to the Punctuation to make it make sense:

Hi, Robin & I have been working on botnets:stegofun! Progress is slow, it's taking a long time, it is time consuming & frustrating

- Could encode most common letters as one symbol, but that would break if crypto were used

* Trade off between frequency of character (more data can be hidden) and ease of writing cover text (Vanna White Problem)


Send a Zip file as an Office doc?
* Upload to Google Docs
* Email to an account that the other end checks
 

SnarlBot Project


SnarlBot
* A simple botnet that uses Social Media/Web 2.0 web apps for "blind drops" as part of the command and control channel
* Content at the blind drops use Steganography so it"s not obviously a botnet doing the communicating
 

Topology
 

This schemes advantages
* The blind drop obfuscates who is controlling the botnet
* Proxies can be used for web traffic to further obfuscate the identity of the bot herder
* Steganography plus encryption makes the channel hard to detect
* Social web sites like Twitter or Facebook are not as likely to be blocked as IRC or P2P
* SSL support for the C&C provided by the web host of the blind drop
Disadvantages
* More data has to be sent to get a message though
* The more complicated something becomes, the more bugs it will have
* May have to simplify the C&C commands
- Use single byte command: "a" for attack
- IPv4 addresses can be expressed in 4 bytes
- This make the Steganography less adaptable, but more meaning can be encoded in less bytes

Isn"t this a little black hat?
Other uses?
* Yep, it"s a little black hat, but who"s to say someone is not already doing it?
* This could start research on how it can be detected.
* May have applications for privacy providing darknets like I2P or Tor
http://www.irongeek.com/i.php?page=videos/darknets-i2p-tor-phreaknic 
Similar Project
* Robin Wood"s KreiosC2
http://www.digininja.org/kreiosc2/index.php

Does not use stego yet, but should be easy to add for someone that knows Ruby
Conclusions/Questions
* Other Steganography techniques?
* Usefulness?
* Detection?
* Other uses for research?
 

 

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