Applied Security Architecture and Threat Models

Applied Security Architecture and Threat Models

Securing Systems

Applied Security Architecture and Threat Models

Securing Systems

Applied Security Architecture and Threat Models

Brook S.E. Schoenfield Forewords by John N. Stewart and James F. Ransome

CRC Press Taylor & Francis Group 6000 Broken Sound Parkway NW, Suite 300 Boca Raton, FL 33487-2742

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v

To the many teachers who’ve pointed me down the path; the managers who have sup- ported my explorations; the many architects and delivery teams who’ve helped to refine the work; to my first design mentors—John Caron, Roddy Erickson, and Dr. Andrew Kerne—without whom I would still have no clue; and, lastly, to Hans Kolbe, who once upon a time was our human fuzzer.

Each of you deserves credit for whatever value may lie herein. The errors are all mine.

Dedication

vii

Contents

Dedication v

Contents vii

Foreword by John N. Stewart xiii

Foreword by Dr. James F. Ransome xv

Preface xix

Acknowledgments xxv

About the Author xxvii

Part I Introduction 3

The Lay of Information Security Land 3 The Structure of the Book 7 References 8

Chapter 1: Introduction 9

1.1 Breach! Fix It! 11 1.2 Information Security, as Applied to Systems 14 1.3 Applying Security to Any System 21 References 25

Chapter 2: The Art of Security Assessment 27

2.1 Why Art and Not Engineering? 28 2.2 Introducing “The Process” 29

viii Securing Systems

2.3 Necessary Ingredients 33 2.4 The Threat Landscape 35

2.4.1 Who Are These Attackers? Why Do They Want to Attack My System? 36

2.5 How Much Risk to Tolerate? 44 2.6 Getting Started 51 References 52

Chapter 3: Security Architecture of Systems 53

3.1 Why Is Enterprise Architecture Important? 54 3.2 The “Security” in “Architecture” 57 3.3 Diagramming For Security Analysis 59 3.4 Seeing and Applying Patterns 70 3.5 System Architecture Diagrams and Protocol Interchange

Flows (Data Flow Diagrams) 73 3.5.1 Security Touches All Domains 77 3.5.2 Component Views 78

3.6 What’s Important? 79 3.6.1 What Is “Architecturally Interesting”? 79

3.7 Understanding the Architecture of a System 81 3.7.1 Size Really Does Matter 81

3.8 Applying Principles and Patterns to Specific Designs 84 3.8.1 Principles, But Not Solely Principles 96

Summary 98 References 98

Chapter 4: Information Security Risk 101

4.1 Rating with Incomplete Information 101 4.2 Gut Feeling and Mental Arithmetic 102 4.3 Real-World Calculation 105 4.4 Personal Security Posture 106 4.5 Just Because It Might Be Bad, Is It? 107 4.6 The Components of Risk 108

4.6.1 Threat 110 4.6.2 Exposure 112 4.6.3 Vulnerability 117 4.6.4 Impact 121

4.7 Business Impact 122 4.7.1 Data Sensitivity Scales 125

Contents ix

4.8 Risk Audiences 126 4.8.1 The Risk Owner 127 4.8.2 Desired Security Posture 129

4.9 Summary 129 References 130

Chapter 5: Prepare for Assessment 133

5.1 Process Review 133 5.1.1 Credible Attack Vectors 134 5.1.2 Applying ATASM 135

5.2 Architecture and Artifacts 137 5.2.1 Understand the Logical and Component Architecture

of the System 138 5.2.2 Understand Every Communication Flow and Any

Valuable Data Wherever Stored 140 5.3 Threat Enumeration 145

5.3.1 List All the Possible Threat Agents for This Type of System 146

5.3.2 List the Typical Attack Methods of the Threat Agents 150 5.3.3 List the System-Level Objectives of Threat Agents

Using Their Attack Methods 151 5.4 Attack Surfaces 153

5.4.1 Decompose (factor) the Architecture to a Level That Exposes Every Possible Attack Surface 154

5.4.2 Filter Out Threat Agents Who Have No Attack Surfaces Exposed to Their Typical Methods 159

5.4.3 List All Existing Security Controls for Each Attack Surface 160

5.4.4 Filter Out All Attack Surfaces for Which There Is Sufficient Existing Protection 161

5.5 Data Sensitivity 163 5.6 A Few Additional Thoughts on Risk 164 5.7 Possible Controls 165

5.7.1 Apply New Security Controls to the Set of Attack Services for Which There Isn’t Sufficient Mitigation 166

5.7.2 Build a Defense-in-Depth 168 5.8 Summary 170 References 171

Part I Summary 173

x Securing Systems

Part II Introduction 179

Practicing with Sample Assessments 179 Start with Architecture 180

A Few Comments about Playing Well with Others 181 Understand the Big Picture and the Context 183

Getting Back to Basics 185 References 189

Chapter 6: eCommerce Website 191

6.1 Decompose the System 191 6.1.1 The Right Level of Decomposition 193

6.2 Finding Attack Surfaces to Build the Threat Model 194 6.3 Requirements 209

Chapter 7: Enterprise Architecture 213

7.1 Enterprise Architecture Pre-work: Digital Diskus 217 7.2 Digital Diskus’ Threat Landscape 218 7.3 Conceptual Security Architecture 221 7.4 Enterprise Security Architecture Imperatives

and Requirements 222 7.5 Digital Diskus’ Component Architecture 227 7.6 Enterprise Architecture Requirements 232 References 233

Chapter 8: Business Analytics 235

8.1 Architecture 235 8.2 Threats 239 8.3 Attack Surfaces 242

8.3.1 Attack Surface Enumeration 254 8.4 Mitigations 254 8.5 Administrative Controls 260

8.5.1 Enterprise Identity Systems (Authentication and Authorization) 261

8.6 Requirements 262 References 266

Contents xi

Chapter 9: Endpoint Anti-malware 267

9.1 A Deployment Model Lens 268 9.2 Analysis 269 9.3 More on Deployment Model 277 9.4 Endpoint AV Software Security Requirements 282 References 283

Chapter 10: Mobile Security Software with Cloud Management 285

10.1 Basic Mobile Security Architectu