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Identify synthetic domain names using Random Forrest Classifier

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DGA Classifier

Context

Once malicious software has been installed on a system it needs to be told what to do. To receive instructions the malware needs to communicate with a command and control server. Historically, the domain name of the command and control server was hardcoded into the code of the malware. This made it very easy for cybersecurity professionals to block this communication channel by blacklisting the domain once they discovered it.

To avoid this weakness malware programs have started to use Domain Generating Algorithms (or DGAs). These algorithms generate a number of random domain names where one of the generated domains is the control server. The infected computed scans through these domains trying to contact each, eventually it will try the correct domain. At this stage, the malware can receive instructions remotely.

Approach

Exploratory Data Analysis

First the given data was explored as documented in EDA Notebook. , with a view to understand:

  • The nature of the data.
  • Potential required pre-processing steps to sanitize the data.
  • Understanding to what extent the classes of legit and dga were present and potential scoring measures.
  • Identifying potential features to get generated.

Feature Generation and Selection

Once the data was better understood and potential features had been identified pipelines implement the desired transformations were developed. Then these pipeline were used to generate different features and their ability to discriminates between the classes was explored. Then feature selection was performed using Principal Component Analysis. The process is document in Feature Generation and Selection Notebook

Model Selection

Finally once suitable features had been identified, then model selection was performed. This was achieved by fitting a number of naive models from a variety of model families. Of the model families fitted, Random Forrest was identified as the most suitable. This information was then carried forward to training by using a Grid Search Cross Validation pipeline wrapping around the Random Forrest Classifier as documentd in Model Selecton Notebook

Installation and Overview of Solution

Run on the Cloud

Open in Cloud Shell

All you need is a Google account, run this repo in a light weight temporary cloud session.

Installation

It is assumed you have Python 3.6 or above installed.

Setup scripts are included for Windows and Linux based environments. The setup scripts do the following

  • Install virtualenv
  • Create a virtualenv .venv
  • Active the virtual env .venv
  • Install the Python packages in requirements.txt
  • Register an IPython kernel as used in the Notebooks
  • Run the unittests with pytest
  • Run the integrationtests with pytest
  • Train the model
  • Runs a simple test of the model
  • Enters an interactive mode where you can query the model

Windows

setup\windows.bat

MacOS and Linux

You may need to set executable permission on the bash script.

sudo chmod +x setup\linux.sh
setup\linux.sh

Usage

If you've run the setup scripts above you will have a trained model ready for use. However if you choose to setup your environment manually here is an overview of the steps that need to be taken.

The following commands assume you're in the root folder of this git repo.

Training the model

Windows

python train_model.py -p data\raw\dga_domains.csv -o models

Linux and MacOS

python train_model.py -p data/raw/dga_domains.csv -o models

The model training script expects at least two parameters to be passed in:

  • -p for the path to the source data.
  • -o where the trained model will be written out.

Testing the model

Windows, Linux, and MacOS

python test_model.py

Runs a trivial test on the model to ensure it has been built.

Querying the model

Windows, Linux, and MacOS

For an interactive session, where you can type in domains

python dga_classify.py -i

To get the prediction for a single or comma separated list of domains

python dga_classify.py reddit,facebook.com,google.co.uk
Query Return Codes
  • 0 - No dga domains were predicted from any of the inputs.
  • 2 - No predictions were made, e.g. empty or invalid inputs.
  • 3 - Dga domains were predicted

Using the return codes it is possible to call this script as part of executing a shell script.

Directory Structure

Data

+---data
|   +---interim
|   +---processed
|   \---raw

The source data is in the raw sub-directory

Tests

+---integrationtests
|   +---models
|   +---test_00_preprocessing
|   +---test_01_feature_generation
|   +---test_02_rescale
|   +---test_04_prepare_model_inputs
|   +---test_05_train_model
|   \---test_06_query_model
...
\---unittests
    +---data
    +---features
    |   \---transformer
    +---pipeline
    |   \---steps
    \---preprocessing
        +---column
        \---text

Source

+---src
|   +---data
|   +---features
|   |   \---transformer
|   +---logging
|   +---model
|   +---pipeline
|   |   \---steps
|   \---preprocessing
|       \---transformer

Each of the sub-directories is exposed as a Python Package.

data

For loading data.

features

Concerned with feature generation, and the sklearn compatible transformer pipelines that implement these feature generators.

logging

Helper package for using built-in logging features.

model

Training, testing, loading, and "querying" the model we've derived from our source data.

pipeline

Separated into complete pipelines and steps for use in pipelines.

preprocessing

Transformations for getting input data into usable state.

Other

+---models
+---notebooks
+---scripts
+---setup

models

This is where built models can be stored. This folder is excluded from git.

Once a model has been trained the following files are written to this folder:

  • report_test.txt - report of test prediction detailing precision, recall, f1-score.
  • report_train.txt - report of training prediction detailing precision, recall, f1-score.
  • trained.model - the persisted model.
  • trained_params.json - the optimal parameters are found via Cross Validated Grid Search.
  • training.log - log file of the training process.

notebooks

Documenting the phases of:

  • Exploratory Data Analysis
  • Feature Generation and Selection
  • Model Selection

scripts

Helper scripts used in development.

setup

Setup scripts.

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