1. Security Architecture and Design
Dr. Bhavani Thuraisingham The University of Texas at Dallas (UTD) June 2013
Security Architecture and Design

2. Domain Agenda System and Components Security
Architectural Security Concepts and Models
Information Systems Evaluation Models

3. Domain Agenda System and Components Security
Architectural Concepts and Definitions
Architectural Security Concepts and Models
Information Systems Evaluation Models

4. Common Security Architecture Terms
Information Security Management System
Information Security Architecture
Best Practice
Architecture
Blueprint
Framework
Infrastructure

5. Objectives of Enterprise Security Architecture
Guidance
Strategically aligned business and security decisions
Provide security-related guidance
Apply security best practices
Define security zones

6. Benefits of an Enterprise Security Architecture
Consistently manage risk
Reduce the costs of managing risk
Accurate security-related decisions
Promote interoperability, integration and ease-of-access
Provide a frame of reference

7. Characteristics of a Good Security Architecture
Strategic
Holistic
Multiple implementations

8. Effects of Poor Architectural Planning
Inability to efficiently support new business services
Unidentified security vulnerabilities
Increased frequency and visibility of security breaches
Poorly understood or coordinated compliance requirements
Poor understanding of security goals and objectives

9. Enterprise Security Architecture Components
Common Architecture Language
Architecture Model
Zachman Framework

10. Zachman Framework Complete overview of IT business alignment
Two-dimensional
Intent
Scope
Principles

11. SABSA What are the business requirements? Contextual Conceptual
Logical
Physical
Component

12. ISO 7498-2 OSI second part About secure communications
NOT an implementation

13. ISO/IEC 4010:2007 Systems and software engineering
Practice for architectural description of software-intensive systems

14. The Open Group Architecture Framework
Governance
Business
Application
Data
Technology

15. Department of Defense Architecture Framework
OMB A-130 requirement
All view
Operational view
Systems view
Technical standards view

16. Which Framework is Right?
Starting place
Culture
Template

17. System and Component Security
Components that provide basic security services
Hardware components
Software components

18. CPU and Processor Privilege States
Supervisor state
Problem state

19. CPU Process States
Running
Ready
Blocked
Masked/interruptible

20. Common Computer Architecture Layers
Application programs
Utilities
Operating system
Computer hardware

21. Common Computer Architecture
Program execution
Access to input/output devices
Controlled access to files and data
Error detection and response
Accounting and tracking
Access for maintenance and troubleshooting

22. Hardware: Computers Mainframe Minicomputer Desktop / server
Laptop / notebook
Embedded

23. Hardware: Communication Devices
Modem
Network Interface Card (NIC)

24. Hardware: Printers Network-aware More than output device
Full operating systems

25. Hardware: Wireless Network interface card Access point Ethernet bridge
Router
Range extender

26. Input/Output (I/O) Devices
I/O Controller
Managing memory
Hardware
Operating system

27. Firmware: Pre-programmed Chips
ROMs (Read-only memory)
PROMs (Programmable read-only memory)
EPROMs (Erasable, programmable, read-only memory)
EEPROMs (Electrically erasable, programmable, read-only memory
Field Programmable Gate Arrays (FPGAs)
Flash chips

28. Software: Operating System
Hardware control
Hardware abstraction
Resource manager

29. CPU and OS Support for Applications
Applications were originally self-contained
OS capable of accommodating more than one application at a time

30. CPU and OS Support for Applications - Today
Today’s applications are portable
Execute multiple process threads
Threads

31. Operating Systems Support for Applications
Multi-tasking
Multi-programming
Multi-processing
Multi-processor
Multi-core

32. Software: Vendor Commercial off the shelf (COTS) Function first
Evaluation

33. Software: Custom Minimal scripting Business application
System life cycle

34. Software: Customer-relationship Management Systems
Business to customer interactions
Tracking habits

35. Systems Architecture Approaches
Open
Closed
Dedicated
Single level
Multi-level
Embedded

36. Architectures: Middleware
Interoperability
Post implementation
Distributed

37. Types of System Memory Resources
CPU registers
Cache
Main memory
Swap space
Disk storage

38. Requirements for Memory Management
Relocation
Protection
Sharing

39. Three Types of Memory Addressing
Logical
Relative
Physical

40. Memory Protection Benefits
Memory reference
Different data classes
Users can share access
Users cannot generate addresses

41. Virtual Memory Extends apparent memory Paging includes Swapping
Splitting physical memory
Splitting programs (processes)
Allocating the required number page frames
Swapping

42. Virtual Machines Mimic the architecture of the actual system
Provided by the operating system

43. Domain Agenda System and Components Security
Architectural Security Concepts and Models
Information Systems Evaluation Models

44. Ring Protection
0. O/S Kernel
I/O
Utilities
User Apps

45. Layering and Data Hiding

46. Privilege Levels Identifying, authenticating and authorizing subjects
Subjects of higher trust
Subjects with lower trust

47. Process Isolation Object’s integrity Prevents interaction
Independent states
Process isolation method

48. Security Architecture
Security critical components of the system
Trusted Computing Base
Reference Monitor and Security Kernel
Security Perimeter
Security Policy
Least Privilege

49. Trusted Computing Base (TCB)
Hardware
Firmware
Software
Processes
Inter-process communications
Simple and Testable

50. Trusted Computing Base (TCB)
Enforces security policy
Monitors four basic functions
Process activation
Execution domain switching
Memory protection
Input/output operations

51. Trusted Computing Base (TCB)
The trusted computing base (TCB) of a computer system is the set of all hardware, firmware, and/or software components that are critical to its security, in the sense that bugs or vulnerabilities occurring inside the TCB might jeopardize the security properties of the entire system. By contrast, parts of a computer system outside the TCB must not be able to misbehave in a way that would leak any more privileges than are granted to them in accordance to the security policy.
The careful design and implementation of a system's trusted computing base is paramount to its overall security. Modern operating systems strive to reduce the size of the TCB so that an exhaustive examination of its code base (by means of manual or computer-assisted software audit or program verification) becomes feasible.

52. Reference Monitor Concept
Abstract machine concept
Must be tamper-proof
Always invoked
Verifiable
Security kernel
Subject
Object

53. Reference Monitor and Security Kernel
In operating systems architecture, a reference monitor is a tamperproof, always-invoked, and small-enough-to-be-fully-tested-and-analyzed module that controls all software access to data objects or devices (verifiable).
The reference monitor verifies that the request is allowed by the access control policy.
For example, Windows 3.x and 9x operating systems were not built with a reference monitor, whereas the Windows NT line, which also includes Windows 2000 and Windows XP, was designed to contain a reference monitor, although it is not clear that its properties (tamperproof, etc.) have ever been independently verified, or what level of computer security it was intended to provide.

54. Domain Agenda System and Components Security
Architectural Security Concepts and Models
Security Models
Information Systems Evaluation Models

55. Bell-LaPadula Confidentiality Model
Hierarchical state machine model
Three fundamental modes
Secure state
Defines access rules

56. Bell and LaPadula
A system state is defined to be "secure" if the only permitted access modes of subjects to objects are in accordance with a security policy. To determine whether a specific access mode is allowed, the clearance of a subject is compared to the classification of the object (more precisely, to the combination of classification and set of compartments, making up the security level) to determine if the subject is authorized for the specific access mode. The clearance/classification scheme is expressed in terms of a lattice. The model defines two mandatory access control (MAC) rules and one discretionary access control (DAC) rule with three security properties:
The Simple Security Property - a subject at a given security level may not read an object at a higher security level (no read-up).
The *-property (read "star"-property) - a subject at a given security level must not write to any object at a lower security level (no write-down). The *-property is also known as the Confinement property.
The Discretionary Security Property - use of an access matrix to specify the discretionary access control.

57. Biba In general, preservation of data integrity has three goals:
Prevent data modification by unauthorized parties
Prevent unauthorized data modification by authorized parties
Maintain internal and external consistency (i.e. data reflects the real world)
Biba security model is directed toward data integrity (rather than confidentiality) and is characterized by the phrase: "no read down, no write up". This is in contrast to the Bell-LaPadula model which is characterized by the phrase "no write down, no read up".
The Biba model defines a set of security rules similar to the Bell-LaPadula model. These rules are the reverse of the Bell-LaPadula rules:
The Simple Integrity Axiom states that a subject at a given level of integrity must not read an object at a lower integrity level (no read down).
The * (star) Integrity Axiom states that a subject at a given level of integrity must not write to any object at a higher level of integrity (no write up).

58. Clark Wilson Model
The Clark-Wilson integrity model provides a foundation for specifying and analyzing an integrity policy for a computing system.
The model is primarily concerned with formalizing the notion of information integrity.
Information integrity is maintained by preventing corruption of data items in a system due to either error or malicious intent.
An integrity policy describes how the data items in the system should be kept valid from one state of the system to the next and specifies the capabilities of various principals in the system.
The model defines enforcement rules and certification rules.
The model’s enforcement and certification rules define data items and processes that provide the basis for an integrity policy. The core of the model is based on the notion of a transaction.

59. Clark Wilson Model
A well-formed transaction is a series of operations that transition a system from one consistent state to another consistent state.
In this model the integrity policy addresses the integrity of the transactions.
The principle of separation of duty requires that the certifier of a transaction and the implementer be different entities.
The model contains a number of basic constructs that represent both data items and processes that operate on those data items. The key data type in the Clark- Wilson model is a Constrained Data Item (CDI). An Integrity Verification Procedure (IVP) ensures that all CDIs in the system are valid at a certain state. Transactions that enforce the integrity policy are represented by Transformation Procedures (TPs). A TP takes as input a CDI or Unconstrained Data Item (UDI) and produces a CDI. A TP must transition the system from one valid state to another valid state. UDIs represent system input (such as that provided by a user or adversary). A TP must guarantee (via certification) that it transforms all possible values of a UDI to a “safe” CDI.

60. Clark Wilson Model
At the heart of the model is the notion of a relationship between an authenticated principal (i.e., user) and a set of programs (i.e., TPs) that operate on a set of data items (e.g., UDIs and CDIs). The components of such a relation, taken together, are referred to as a Clark-Wilson triple. The model must also ensure that different entities are responsible for manipulating the relationships between principals, transactions, and data items. As a short example, a user capable of certifying or creating a relation should not be able to execute the programs specified in that relation.
The model consists of two sets of rules: Certification Rules (C) and Enforcement Rules (E). The nine rules ensure the external and internal integrity of the data items. To paraphrase these:
C1—When an IVP is executed, it must ensure the CDIs are valid. C2—For some associated set of CDIs, a TP must transform those CDIs from one valid state to another. Since we must make sure that these TPs are certified to operate on a particular CDI, we must have E1 and E2.

61. Clark Wilson Model
E1—System must maintain a list of certified relations and ensure only TPs certified to run on a CDI change that CDI. E2—System must associate a user with each TP and set of CDIs. The TP may access the CDI on behalf of the user if it is “legal.” This requires keeping track of triples (user, TP, {CDIs}) called “allowed relations.”
C3—Allowed relations must meet the requirements of “separation of duty.” We need authentication to keep track of this.
E3—System must authenticate every user attempting a TP. Note that this is per TP request, not per login. For security purposes, a log should be kept.
C4—All TPs must append to a log enough information to reconstruct the operation. When information enters the system it need not be trusted or constrained (i.e. can be a UDI). We must deal with this appropriately.
C5—Any TP that takes a UDI as input may only perform valid transactions for all possible values of the UDI. The TP will either accept (convert to CDI) or reject the UDI. Finally, to prevent people from gaining access by changing qualifications of a TP:
E4—Only the certifier of a TP may change the list of entities associated with that TP.

62. Other Fundamental Models
Information flow model
Non-interference model
State machine
Lattice-based model
Graham-Denning
Harrison-Ruzzo-Ullman result

63. Domain Agenda System and Components Security
Architectural Security Concepts and Models
Information Systems Evaluation Models

64. Evaluation Roles
Buyer/Customer
Seller/Vendor
Lab/Certifier

65. Documents & Organizations
TCSEC (U.S DoD)
ITSEC (European Union)
Common Criteria (ISO Standard I5408)

66. TCSEC or Orange Book DoD-centric Security and functionality
Product evaluation

67. Secure System Evaluation: TCSEC
Trusted Computer System Evaluation Criteria (TCSEC) is a United States Government Department of Defense (DoD) standard that sets basic requirements for assessing the effectiveness of computer security controls built into a computer system. The TCSEC was used to evaluate, classify and select computer systems being considered for the processing, storage and retrieval of sensitive or classified information.
The TCSEC, frequently referred to as the Orange Book, is the centerpiece of the DoD Rainbow Series publications. Initially issued in 1983 by the National Computer Security Center (NCSC), an arm of the National Security Agency, and then updated in 1985,.
TCSEC was replaced by the Common Criteria international standard originally published in 2005.

68. Secure System Evaluation: TCSEC
Policy - The security policy must be explicit, well-defined and enforced by the computer system. There are two basic security policies:
Mandatory Security Policy - Enforces access control rules based directly on an individual's clearance, authorization for the information and the confidentiality level of the information being sought. Other indirect factors are physical and environmental. This policy must also accurately reflect the laws, general policies and other relevant guidance from which the rules are derived.
Marking - Systems designed to enforce a mandatory security policy must store and preserve the integrity of access control labels and retain the labels if the object is exported.
Discretionary Security Policy - Enforces a consistent set of rules for controlling and limiting access based on identified individuals who have been determined to have a need-to-know for the information.

69. Secure System Evaluation: TCSEC
Accountability - Individual accountability regardless of policy must be enforced. A secure means must exist to ensure the access of an authorized and competent agent which can then evaluate the accountability information within a reasonable amount of time and without undue difficulty. There are three requirements under the accountability objective:
Identification - The process used to recognize an individual user.
Authentication - The verification of an individual user's authorization to specific categories of information.
Auditing - Audit information must be selectively kept and protected so that actions affecting security can be traced to the authenticated individual.
The TCSEC defines four divisions: D, C, B and A where division A has the highest security. Each division represents a significant difference in the trust an individual or organization can place on the evaluated system. Additionally divisions C, B and A are broken into a series of hierarchical subdivisions called classes: C1, C2, B1, B2, B3 and A1.

70. Secure System Evaluation: TCSEC
Assurance: The computer system must contain hardware/software mechanisms that can be independently evaluated to provide sufficient assurance that the system enforces the above requirements. By extension, assurance must include a guarantee that the trusted portion of the system works only as intended. To accomplish these objectives, two types of assurance are needed with their respective elements:
Assurance Mechanisms : Operational Assurance: System Architecture, System Integrity, Covert Channel Analysis, Trusted Facility Management and Trusted Recovery
Life-cycle Assurance : Security Testing, Design Specification and Verification, Configuration Management and Trusted System Distribution

71. ITSEC
International origin
ITSEM
Functionality
Assurance

72. Secure System Evaluation: ITSEC
The Information Technology Security Evaluation Criteria (ITSEC) is a structured set of criteria for evaluating computer security within products and systems. The ITSEC was first published in May 1990 in France, Germany, the Netherlands, and the United Kingdom based on existing work in their respective countries. Following extensive international review, Version 1.2 was subsequently published in June 1991 by the Commission of the European Communities for operational use within evaluation and certification schemes.
Levels E1 – E6

73. Common Criteria
Origins
ISO
Documents
EAL I-7 PP
TEO ST

74. Secure System Evaluation: Common Criteria
The Common Criteria for Information Technology Security Evaluation (abbreviated as Common Criteria or CC) is an international standard (ISO/IEC ) for computer security certification.
Common Criteria is a framework in which computer system users can specify their security functional and assurance requirements, vendors can then implement and/or make claims about the security attributes of their products, and testing laboratories can evaluate the products to determine if they actually meet the claims. In other words, Common Criteria provides assurance that the process of specification, implementation and evaluation of a computer security product has been conducted in a rigorous and standard manner.
Levels: EAL 1 – EAL 7 (Evaluation Assurance Levels)

75. EAL = $ In natural language
A user has only one password and is assigned only one role.
A valid password is a case-sensitive string of from six to eight single-byte alphanumeric characters.
A user must set up a password at the 1st-time login.
The system allows the authenticated user to change his password.
The new password cannot be the same as the old one.

76. Comparison of Evaluation Levels
Common Criteria
US TCSEC
European ITSEC --
D: Minimal Protection EO
EAL 1
EAL 2
C1: Discretionary Security Protection E1
EAL 3
C2: Controlled Access Protection E2
EAL 4
B1: Labeled Security Protection E3
EAL 5
B2: Structure Prote4ction E4
EAL 6
B3: Security Domains E5
EAL 7
A1: Verified Design E6

77. Certification and Accreditation
Certification and Accreditation (C&A) is a process for implementing information security. It is a systematic procedure for evaluating, describing, testing and authorizing systems prior to or after a system is in operation.
Certification is a comprehensive assessment of the management, operational, and technical security controls in an information system, made in support of security accreditation, to determine the extent to which the controls are implemented correctly, operating as intended, and producing the desired outcome with respect to meeting the security requirements for the system.
Accreditation is the official management decision given by a senior agency official to authorize operation of an information system and to explicitly accept the risk to agency operations (including mission, functions, image, or reputation), agency assets, or individuals, based on the implementation of an agreed-upon set of security controls.

78. Popular Management Frameworks
ISO 27001
ITIL
COSO
CMMI

79. ISO 27001 – Stages in Implementing an ISMS
Define information security policy
Define scope of ISMS
Perform risk assessment
Manage risks
Select controls
Prepare statement of applicability

80. IT Infrastructure Library (ITIL)
Focuses on IT services
Seven main sections
Supporting products

81. Committee of Sponsoring Organizations
Emphasizes the importance of identifying and managing risks
Process
People
Reasonable assurance
Objectives

82. Capability Maturity Model
Developed by SEI
Based on TQM concepts
Framework for improving process
Benefits

83. Open vs. Closed System
Open systems allow users to reuse, edit, manipulate, and contribute to the system development
Open source software is an example of Open systems
Licensed to the public
Freeware is also an example of Open systems
Closed systems permits users to use the system as it is

84. Some Security Threats Buffer Overflow Maintenance Hooks
Time of check / Time of use attacks