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Guidelines to make Data Flow Diagram for Threat Modeling

Published on: 8/14/2014
Topic: Web Application Security
Data Flow Diagram can be used effectively during Threat Modeling exercise. We first create high level DFDs and break further to clarify the context.

Guidelines to make Data Flow Diagram for Threat Modeling

Start with high level DFD and then break further

1. The top level DFD should be Context driven showing external user interaction with the whole system/product across top level/external trust boundry.
2. The next level break up may focus on one specific use case or feature
3. The lowest level DFD should be preapred only if required that may show all the components within same trust boundry.

Diagram Approach:

Option 1 – Top Down approach: You may take top down approach to start with the whole system further detailed down by specific use cases or features

Option 2: Bottom Up Approach: Start with specific feature/data element and anslyse bottom to top, finding all the entry-exit points in appliaction that influence the respective feature/data element. This may be used if you want to first focus on highly critical functions/data elements first. For example if your application handles Credit Card data of your customers then you may start by analysing all touch points in your application that are only relevant to CC data.

DFD Symbols

Item Symbol
Data flow One way arrow
Data store Two parallel horizontal lines
Process Circle
Multi-process Two concentric circles
Interactors Rectangle
Trust boundary Dotted line

Application of Threat Category

  Element     Spoofing   Data Tampering   Repudiation   Information Disclosure   Denial of Service   Elevation of Privilege    
Data Flows       
Data Stores       
Processes 
Interactors         

Note: DFD is not a Flow Chart or Class Diagram or a Sequence Diagram.


Read Threat Modeling - Practice Guide to understand how to use DFD during Threat Modeling exercise.


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