Securing Systems: Applied Security Architecture and Threat Models, 1st Edition (Hardback) book cover

Securing Systems

Applied Security Architecture and Threat Models, 1st Edition

By Brook S. E. Schoenfield

CRC Press

440 pages | 50 B/W Illus.

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pub: 2015-05-20
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Internet attack on computer systems is pervasive. It can take from less than a minute to as much as eight hours for an unprotected machine connected to the Internet to be completely compromised. It is the information security architect’s job to prevent attacks by securing computer systems. This book describes both the process and the practice of assessing a computer system’s existing information security posture. Detailing the time-tested practices of experienced security architects, it explains how to deliver the right security at the right time in the implementation lifecycle.

Securing Systems: Applied Security Architecture and Threat Models covers all types of systems, from the simplest applications to complex, enterprise-grade, hybrid cloud architectures. It describes the many factors and prerequisite information that can influence an assessment. The book covers the following key aspects of security analysis:

  • When should the security architect begin the analysis?
  • At what points can a security architect add the most value?
  • What are the activities the architect must execute?
  • How are these activities delivered?
  • What is the set of knowledge domains applied to the analysis?
  • What are the outputs?
  • What are the tips and tricks that make security architecture risk assessment easier?

To help you build skill in assessing architectures for security, the book presents six sample assessments. Each assessment examines a different type of system architecture and introduces at least one new pattern for security analysis. The goal is that after you’ve seen a sufficient diversity of architectures, you’ll be able to understand varied architectures and can better see the attack surfaces and prescribe security solutions.


"Brook Schoenfield has distilled a tremendous amount of practical experience and critical thinking about security architecture into a resource that should be extremely helpful to practitioners."

— Jack Jones, Originator of The Open Group Standard, Factor Analysis for Information Risk (FAIR)

"Five stars for Brook Schoenfield who has created a one-stop resource for both the security strategist/technologist and the executive suite, sounding the ‘proactive’ klaxon. The reader is given substantive exemplars on the practicality of architecting security solutions into the mix from the get-go, and obviating the tendency to ‘bolt on’ security at a later date. Securing Systems should be on every CSO’s and CISO’s desk, and referenced often as teams are built and security solutions architected."

— Christopher Burgess, CEO, Prevendra Inc, Author of Secrets Stolen, Fortunes Lost and Protecting Intellectual Property

"Brook Schoenfield’s approach to securing systems addresses the entire enterprise, not only its digital systems, as well as the processes and people who will interact, design, and build the systems. This book fills a significant gap in the literature and is appropriate for use as a resource for both aspiring and seasoned security architects alike."

— Dr. James F. Ransome, CISSP, CISM, Senior Director of Product Security at Intel Security Group and Co-Author of Core Software Security

"It is not good enough just to build something and try and secure it, it must be architected from the bottom up with security in it, by professionally trained and skilled security architects, checked and validated by regular assessments for weakness, and through a learning system that learns from today to inform tomorrow. We must succeed."

— John N. Stewart, SVP & Chief Security Officer, Cisco Security and Trust Organization and Winner of the CSO 40 Silver Award for the 2014 Chief Security Officer of the Year

"This book describes well why some companies are successful and some are not in the area of software security. Brook writes this book out of his own experiences from many years in the trade. I doubt that you can find many who have more years of great achievements in his field. By reading this book, you will get a fast track to build competence in a very advanced area. The possibilities to take the wrong route are much wider than you can imagine. Please do like me— read it and think how I can improve my daily business from what I have learned."

— Per-Olof Persson, Head of Software Security, Sony Mobile

Table of Contents



Foreword by John N. Stewart

Foreword by Dr. James F. Ransome



About the Author

Part I Introduction

The Lay of Information Security Land

The Structure of the Book



Breach! Fix It!

Information Security, as Applied to Systems

Applying Security to Any System


The Art of Security Assessment

Why Art and Not Engineering?

Introducing "The Process"

Necessary Ingredients

The Threat Landscape

Who Are These Attackers? Why Do They Want to Attack My System?

How Much Risk to Tolerate?

Getting Started


Security Architecture of Systems

Why Is Enterprise Architecture Important?

The "Security" in "Architecture"

Diagramming For Security Analysis

Seeing and Applying Patterns

System Architecture Diagrams and Protocol Interchange Flows (Data Flow Diagrams)

Security Touches All Domains

Component Views

What’s Important?

What Is "Architecturally Interesting"?

Understanding the Architecture of a System

Size Really Does Matter

Applying Principles and Patterns to Specific Designs

Principles, But Not Solely Principles



Information Security Risk

Rating with Incomplete Information

Gut Feeling and Mental Arithmetic

Real-World Calculation

Personal Security Posture

Just Because It Might Be Bad, Is It?

The Components of Risk





Business Impact

Data Sensitivity Scales

Risk Audiences

The Risk Owner

Desired Security Posture



Prepare for Assessment

Process Review

Credible Attack Vectors

Applying ATASM

Architecture and Artifacts

Understand the Logical and Component Architecture of the System

Understand Every Communication Flow and Any Valuable Data Wherever Stored

Threat Enumeration

List All the Possible Threat Agents for This Type of System

List the Typical Attack Methods of the Threat Agents

List the System-Level Objectives of Threat Agents Using Their Attack Methods

Attack Surfaces

Decompose (factor) the Architecture to a Level That Exposes Every Possible Attack Surface

Filter Out Threat Agents Who Have No Attack Surfaces Exposed to Their Typical Methods

List All Existing Security Controls for Each Attack Surface

Filter Out All Attack Surfaces for Which There Is Sufficient Existing Protection

Data Sensitivity

A Few Additional Thoughts on Risk

Possible Controls

Apply New Security Controls to the Set of Attack Services for Which There Isn’t Sufficient Mitigation

Build a Defense-in-Depth



Part I Summary

Part II Introduction

Practicing with Sample Assessments

Start with Architecture

A Few Comments about Playing Well with Others

Understand the Big Picture and the Context

Getting Back to Basics


eCommerce Website

Decompose the System

The Right Level of Decomposition

Finding Attack Surfaces to Build the Threat Model


Enterprise Architecture

Enterprise Architecture Pre-work: Digital Diskus

Digital Diskus’ Threat Landscape

Conceptual Security Architecture

Enterprise Security Architecture Imperatives and Requirements

Digital Diskus’ Component Architecture

Enterprise Architecture Requirements


Business Analytics



Attack Surfaces

Attack Surface Enumeration


Administrative Controls

Enterprise Identity Systems (Authentication and Authorization)



Endpoint Anti-malware

A Deployment Model Lens


More on Deployment Model

Endpoint AV Software Security Requirements


Mobile Security Software with Cloud Management

Basic Mobile Security Architecture

Mobility Often Implies Client/Cloud

Introducing Clouds

Authentication Is Not a Panacea

The Entire Message Stack Is Important

Just Good Enough Security

Additional Security Requirements for a Mobile and Cloud Architecture

Cloud Software as a Service (SaaS)

What’s So Special about Clouds?

Analysis: Peel the Onion

Freemium Demographics

Protecting Cloud Secrets

The Application Is a Defense


Additional Requirements for the SaaS Reputation Service 319


Part II Summary

Part III Introduction

Patterns and Governance Deliver Economies of Scale

Expressing Security Requirements

Expressing Security Requirements to Enable

Who Consumes Requirements?

Getting Security Requirements Implemented

Why Do Good Requirements Go Bad?

Some Thoughts on Governance



Building an Assessment Program

Building a Program

Senior Management’s Job

Bottom Up?

Use Peer Networks

Building a Team


Documentation and Artifacts

Peer Review


Mistakes and Missteps

Not Everyone Should Become an Architect

Standards Can’t Be Applied Rigidly

One Size Does Not Fit All, Redux

Don’t Issue Edicts Unless Certain of Compliance

Measuring Success

Invitations Are Good!

Establish Baselines



Part III Summary and Afterword




About the Author

Brook S.E. Schoenfield is Director of Product Security Architecture at Intel Security Group. He is the senior technical leader for software security across the division’s broad product portfolio. He has held leadership security architecture positions at high-tech companies for many years. Brook has presented at conferences such as RSA, BSIMM, and SANS What Works Summits on subjects within security architecture, including architecture risk assessment and threat models, information security risk, SaaS/Cloud security, and Agile security. He has been published by CRC Press, SANS, Cisco, and the IEEE.

Subject Categories

BISAC Subject Codes/Headings:
COMPUTERS / Software Development & Engineering / General
COMPUTERS / Software Development & Engineering / Systems Analysis & Design
COMPUTERS / Security / General