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Docker for Automating Honeypots or Malware Sandboxes

Disclaimer: Docker is not super secure for isolation. This post aims to show not-so-well-known Docker features and how they could be used in other contexts.

Docker has become very popular in the last few years for being such a flexible tool to isolate processes in so-called containers. If you haven't played with it yet, I highly recommend you to watch my free course on Docker Security. But if you have, I'd like to give you an insight that provides significant value for automating honeypots or malware sandboxes. I'm talking about 'docker diff' and how to dynamically spot changes on it.

$ docker diff <container_name>

It's possible to keep track of every file changed in a container since its creation from an image. This way, it's possible to know what files the attacker/malware has created, modified, or deleted. Here's an example: let's create a container from an Ubuntu image and leave it running using sleep.

$ docker run --name my_sandbox --detach ubuntu sleep 2000

Let's check if it's running:

$ docker ps
CONTAINER ID        IMAGE               COMMAND             NAMES
fc04fa5bf6a4        ubuntu              "sleep 2000"        my_sandbox

Okay, it's running. Let's try docker diff to see if any files were changed after we used the 'sleep' command.

$ docker diff my_sandbox
# No output

It turns out that 'sleep' doesn't create, modify, or delete any files. Let's create one file in this container then:

$ docker exec my_sandbox touch /tmp/test
# No output

Okay, file created. Let's see if docker diff shows something now:

$ docker diff my_sandbox
C /tmp
A /tmp/test

Here it is, a new directory (/tmp) and a new file (/tmp/test). It's empty, but let's copy it anyways to our host machine using docker cp.

$ docker cp my_sandbox:/tmp/test ./test
# No output

File copied!

But the problem is, in case we want to automate this process, for example, to send every new file to VirusTotal, how could we get notified when a file is created? We have a few options:

  • Perform pooling in docker diff <container_name>
  • Share a volume between Docker host and container and use tools like inotify-tools or pyinotify.

Using pyinotify

Let's use pyinotify to see an example. After installing it, open 2 tabs in your terminal. In the first, start the container, and in the second, start the pyinotify script to monitor the files located in the shared volume.

$ # First Tab
$ docker run --name my_sandbox --detach -v "$(pwd)/deleteme:/app" ubuntu sleep 2000

Container started sharing the volume deleteme relative to the current directory $(pwd).

$ # Second Tab
$ vim monitor.py

Time to add the content of our monitor.py file:


import pyinotify
import subprocess

# Directory to watch
# We'll use the shared volume with Docker container
directory_to_watch = '/home/anderson/deleteme/'

def onChange(ev):
    # Print changed file on the screen
    # But could be your code to upload the file to VirusTotal
    # Or anything you want
    cmd = ['/bin/echo', 'File', ev.pathname, 'changed']

wm = pyinotify.WatchManager()
wm.add_watch(directory_to_watch, pyinotify.IN_CLOSE_WRITE, onChange)
notifier = pyinotify.Notifier(wm)

Then we run it to monitor our files:

$ # Second Tab
$ python monitor.py

Okay, time to go back to Tab #1 and create some files from within the container:

$ # First Tab
$ docker exec -it my_sandbox touch /app/oi

Great, the file is created. Let's check the output of our python script:

$ # Second Tab
$ python monitor.py 
File /home/anderson/deleteme/oi changed

As you can see, the file creation was detected. It also works with modifications to existing files.

This is just the beginning, of course. We would need to intercept network requests by configuring a proxy in Docker settings, get the logs from the container and perform some analysis on them, and come up with more ideas to analyze container activity without placing agents or anything inside it. This way, the difference between a non-honeypot and a honeypot/malware sandbox will become less and less apparent.

Edit: You may want to read the next post: Preventing Docker Escaping Attacks

That's all for today. Thank you!

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