To effectively assess the security needs of an organization and to evaluate and choose various security products and policies, the manager responsible for security needs some systematic way of defining the requirements for security and characterizing the approaches to satisfy those requirements. This process is difficult enough in a centralized data processing environment; with the use of local- and wide-area networks (LANs and WANs, respectively), the problems are compounded.
The challenges for management in providing information security are formidable. Even for relatively small organizations, information system assets are substantial, including databases and files related to personnel, company operation, financial matters, and so on. Typically, the information system environment is complex, including a variety of storage systems, servers, workstations, local networks, and Internet and other remote network connections. Managers face a range of threats always growing in sophistication and scope. And the range of consequences for security failures, both to the company and to individual managers, is substantial, including financial loss, civil liability, and even criminal liability.
Standards for providing information system security become essential in such circumstances. Standards can define the scope of security functions and features needed, policies for managing information and human assets, criteria for evaluating the effectiveness of security measures, techniques for ongoing assessment of security and for the ongoing monitoring of security breaches, and procedures for dealing with security failures.
Figure 1, based on , suggests the elements that, in an integrated fashion, constitute an effective approach to information security management. The focus of this approach is on two distinct aspects of providing information security: process and products.
looks at information security from the point of view of management policies, procedures, and controls.
focuses on technical aspects and is concerned with the use of certified products in the IT environment when possible. In Figure 1, the term
refers to specifications that refer to aspects such as IT network security, digital signatures, access control, nonrepudiation, key management, and hash functions. Operational, management, and technical
encompass policies and practices that are defined and enforced by management. Examples include personnel screening policies, guidelines for classifying information, and procedures for assigning user IDs.
Management system audits, certification, and accreditation
deals with management policies and procedures for auditing and certifying information security products.
Codes of practice
refer to specific policy standards that define the roles and responsibilities of various employees in maintaining information security.
deals with product and system testing and evaluation.
Cultural, ethical, social, and legal issuers
refer to human factors aspects related to information security.
Figure 1: Information Security Management Elements
Many standards and guideline documents have been developed in recent years to aid management in the area of information security. The two most important are ISO 17799, which deals primarily with process security, and the
which deals primarily with product security. This article surveys these two standards, and examines some other important standards and guidelines as well.
An increasingly popular standard for writing and implementing security policies is ISO 17799 "Code of Practice for Information Security Management." (ISO 17799 will eventually be reissued as ISO 27002 in the new ISO 27000 family of security standards). ISO 17799 is a comprehensive set of controls comprising best practices in information security. It is essentially an internationally recognized generic information security standard. Table 1 summarizes the area covered by this standard and indicates the objectives for each area.
Table 1: ISO 17799 Areas and Objectives
Provide management direction and support for information security in accordance with
business requirements and relevant laws and regulations.
Organization of Information Security
Manage information security within the organization. Maintain the security of the organization's information and information processing facilities that are accessed,
processed, communicated to, or managed by external parties.
Achieve and maintain appropriate protection of organizational assets. Ensure that
information receives an appropriate level of protection.
Human Resources Security
Ensure that employees, contractors, and third-party users (1) understand their responsibilities and are suitable for the roles they are considered for; (2) are aware of information security threats and concerns; (3) exit an organization or
change employment in an orderly manner
Physical and Environmental Security
Prevent unauthorized physical access, damage, and interference to the organizations premises and information. Prevent loss, damage, theft, or
compromise of assets and interruption to the organization's activities.
Communications and Operations Management
Develop controls for operational procedures, third-party service delivery management, system planning, malware protection, backup, network security management, media handling, information exchange, e-commerce services,
Develop controls for business requirements for user access, user responsibilities, network access control, OS access control, application access control, and
information access control.
Information Systems Acquisition, Development, and Maintenance
Develop controls for correct processing in applications, cryptographic functions,
system file security, support process security, and vulnerability management.
Information Security Incident Management
Ensure information security events and weaknesses associated with information systems are communicated in a manner that allows timely corrective action to be taken. Ensure a consistent and effective approach is applied to the management
of information security incidents.
Business Continuity Management
Counteract interruptions to business activities to protect critical business processes from the effects of major failures of information systems or disasters
and to ensure their timely resumption.
Avoid breaches of any law, statutory, regulatory, or contractual obligations, and of any security requirements. Ensure compliance of systems with organizational security policies and standards. Maximize the effectiveness of
and minimize interference to and from the information systems audit process.
With the increasing interest in security, ISO 17799 certification, provided by various accredited bodies, has been established as a goal for many corporations, government agencies, and other organizations around the world. ISO 17799 offers a convenient framework to help security policy writers structure their policies in accordance with an international standard.
Much of the content of ISO 17799 deals with security controls, which are defined as practices, procedures, or mechanisms that may protect against a threat, reduce a vulnerability, limit the effect of an unwanted incident, detect unwanted incidents, and facilitate recovery. Some controls deal with security management, focusing on management actions to institute and maintain security policies. Other controls are operational; they address the correct implementation and use of security policies and standards, ensuring consistency in security operations and correcting identified operational deficiencies. These controls relate to mechanisms and procedures that are primarily implemented by people rather than systems.
Finally, there are technical controls; they involve the correct use of hardware and software security capabilities in systems. These controls range from simple to complex measures that work together to secure critical and sensitive data, information, and IT systems functions. This concept of controls cuts across all the areas listed in Table 1.
To give some idea of the scope of ISO 17799, we examine several of the security areas discussed in that document.
is a key security management function that is addressed in multiple areas within the document. First, ISO 17799 lists key data items that should, when relevant, be included in an audit log:
Dates, times, and details of key events, for example, log-on and log-off
Records of successful and rejected system access attempts
Records of successful and rejected data and other resource access attempts
Changes to system configuration
Use of privileges
Use of system utilities and applications
Files accessed and the kind of access
Network addresses and protocols
Alarms raised by the access control system
Activation and deactivation of protection systems, such as antivirus systems and intrusion detection systems
It provides a useful set of guidelines for implementation of an auditing capability:
Audit requirements should be agreed upon by appropriate management.
The checks should be limited to read-only access to software and data.
Access other than read-only should be allowed only for isolated copies of system files, which should be erased when the audit is completed or given appropriate protection if there is an obligation to keep such files under audit documentation requirements.
Resources for performing the checks should be explicitly identified and made available.
Requirements for special or additional processing should be identified and agreed upon.
All access should be monitored and logged to produce a reference trail; the use of timestamped reference trails should be considered for critical data or systems.
All procedures, requirements, and responsibilities should be documented.
The person(s) carrying out the audit should be independent of the activities audited.
Under the area of communications and operations management, ISO 17799 includes network security management. One aspect of this management is concerned with network controls for networks owned and operated by the organization. The document provides implementation guidance for these in-house networks. An example of a control follows: Restoration procedures should be regularly checked and tested to ensure that they are effective and that they can be completed within the time allotted in the operational procedures for recovery. Similarly, the document provides guidance for security controls for network services provided by outside vendors. An example of guidance in this area follows: The ability of the network service provider to manage agreed-upon services in a secure way should be determined and regularly monitored, and the right to audit should be agreed upon.
As can be seen, some ISO 17700 specifications are detailed and specific, whereas others are quite general.
The Common Criteria for Information Technology Security Evaluation (CC) is a joint international effort by numerous national standards organizations and government agencies [3,4,5]. U.S. participation is by the
National Institute of Standards and Technology (NIST) and the National Security Agency NSA). CC defines a set of IT requirements of known validity that can be used in establishing security requirements for prospective products and systems. The CC also defines the
Protection Profile (PP) construct that allows prospective consumers or developers to create standardized sets of security requirements that will meet their needs.
The aim of the CC specification is to provide greater confidence in the security of IT products as a result of formal actions taken during the process of developing, evaluating, and operating these products. In the development stage, the CC defines sets of IT requirements of known validity that can be used to establish the security requirements of prospective products and systems. Then the CC details how a specific product can be evaluated against these known requirements, to provide confirmation that it does indeed meet them, with an appropriate level of confidence. Lastly, when in operation the evolving IT environment may reveal new vulnerabilities or concerns. The CC details a process for responding to such changes, and possibly reevaluating the product.
Following successful evaluation, a particular product may be listed as CC certified or validated by the appropriate national agency, such as NIST or NSA in the United States. That agency publishes lists of evaluated products, which are used by government and industry purchasers who need to use such products.
The CC defines a common set of potential security requirements for use in evaluation. The term Target of Evaluation (TOE) refers to that part of the product or system that is subject to evaluation. The requirements fall into two categories:
Define desired security behavior. CC documents establish a set of security functional components that provide a standard way of expressing the security functional requirements for a TOE.
Assurance requirements: The basis for gaining confidence that the claimed security measures are effective and implemented correctly. CC documents establish a set of assurance components that provide a standard way of expressing the assurance requirements for a TOE.
Both functional requirements and assurance requirements are organ-ized into classes: A class is a collection of requirements that share a common focus or intent. Each of these classes contains numerous families. The requirements within each
family share security objectives but differ in emphasis or rigor. For example, the audit class contains six families dealing with various aspects of auditing (for example, audit data generation, audit analysis, and audit event storage). Each family, in turn, contains one or more components. A
component describes a specific set of security requirements and is the smallest selectable set of security requirements for inclusion in the structures defined in the CC.
For example, the cryptographic support class of functional re-quirements includes two families: cryptographic key management and cryptographic operation. The cryptographic key management family has four components, which are used to specify key generation algorithm and key size; key distribution method; key access method; and key destruction method. For each component, a standard may be referenced to define the requirement. Under the cryptographic operation family, there is a single component, which specifies an algorithm and key size based on a an assigned standard.
Sets of functional and assurance components may be grouped to-gether into reusable packages, which are known to be useful in meeting identified objectives. An example of such a package would be functional components required for
Discretionary Access Controls.
The CC also defines two kinds of documents that can be generated using the CC-defined requirements.
Protection profiles (PPs): Define an implementation-independent set of security requirements and objectives for a category of products or systems that meet similar consumer needs for IT security. A PP is intended to be reusable and to define requirements that are known to be useful and effective in meeting the identified objectives. The PP concept has been developed to support the definition of functional standards and as an aid to formulating procurement specifications. The PP reflects user security requirements.
Security targets (STs): Contain the IT security objectives and requirements of a specific identified TOE and define the functional and assurance measures offered by that TOE to meet stated requirements. The ST may claim conformance to one or more PPs and forms the basis for an evaluation. The ST is supplied by a vendor or developer.
Figure 2 illustrates the relationship between requirements on the one hand and profiles and targets on the other. For a PP, a user can select many components to define the requirements for the desired product. The user may also refer to predefined packages that assemble numerous requirements commonly grouped together within a product requirements document. Similarly, a vendor or designer can select numerous components and packages to define an ST.
Figure 2: Organization and Construction of Common Criteria Requirements
As an example for the use of the CC, consider the smart card. The protection profile for a smart card, developed by the
Smart Card Security User Group,
provides a simple example of a PP. This PP describes the IT security requirements for a smart card to be used in connection with sensitive applications, such as banking industry financial payment systems. The assurance level for this PP is
Evaluation Assurance Level
(EAL) 4, which is described subsequently. The PP lists threats that must be addressed by a product that claims to comply with this PP. The threats include the following:
May entail reading data from the TOE through techniques commonly employed in
Integrated Circuit (IC)
failure analysis and IC reverse engineering efforts.
Invalid input may take the form of operations that are not formatted correctly, requests for information beyond register limits, or attempts to find and execute undocumented commands. The result of such an attack may be a compromise in the security functions, generation of exploitable errors in operation, or release of protected data.
Linkage of multiple operations:
An attacker may observe multiple uses of resources or services and, by linking these observations, deduce information that may reveal security function data.
Following a list of threats, the PP turns to a description of
which reflect the stated intent to counter identified threats or comply with any organizational security policies identified. Nineteen objectives are listed, including the following:
The system must provide the means of recording selected security-relevant events, so as to assist an administrator in the detection of potential attacks or misconfiguration of the system security features that would leave it susceptible to attack.
The system must be resistant to repeated probing through insertion of erroneous data.
The system must provide the means of controlling and limiting the leakage of information in the system so that no useful information is revealed over the power, ground, clock, reset, or I/O lines.
are provided to thwart specific threats and to support specific policies under specific assumptions. The PP lists specific requirements in three general areas: TOE security functional requirements, TOE security assurance requirements, and security requirements for the IT environment. In the area of
security functional requirements,
the PP defines 42 requirements from the available classes of security functional requirements.
For example, for security auditing, the PP stipulates what the system must audit; what information must be logged; what the rules are for monitoring, operating, and protecting the logs; and so on. Functional requirements are also listed from the other functional requirements classes, with specific details for the smart card operation.
The PP defines 24
security assurance requirements
from the available classes of security assurance requirements. These requirements were chosen to demonstrate:
The quality of the product design and configuration
That adequate protection is provided during the design and implementation of the product
That vendor testing of the product meets specific parameters
That security functions are not compromised during product delivery
That user guidance, including product manuals pertaining to installation, maintenance, and use, are of a specified quality and appropriateness
The PP also lists
Security Requirements of the IT Environment
. They cover the following topics:
Cryptographic key distribution
Cryptographic key destruction
The final section of the PP (excluding appendices) is a lengthy rationale for all the selections and definitions in the PP. The PP is an industrywide effort designed to be realistic in its ability to be met by a variety of products with a variety of internal mechanisms and implementation approaches.
The concept of
is a difficult one to define. Further, the degree of assurance required varies from one context and one function to another. To structure the need for assurance, the CC defines a scale for rating assurance consisting of seven EALs ranging from the least rigor and scope for assurance evidence (EAL 1) to the most (EAL 7). The levels are as follows:
EAL 1: Functionally tested:
For environments where security threats are not considered serious. It involves independent product testing with no input from the product developers. The intent is to provide a level of confidence in correct operation.
EAL 2: Structurally tested:
Includes a review of a high-level design provided by the product developer. Also, the developer must conduct a vulnerability analysis for well-known flaws. The intent is to provide a low to moderate level of independently assured security.
EAL 3: Methodically tested and checked:
Requires a focus on the security features, including requirements that the design separate security-related components from those that are not; that the design specifies how security is enforced; and that testing be based both on the interface and the high-level design, rather than a black box testing based only on the interface. It is applicable where the requirement is for a moderate level of independently assured security, with a thorough investigation of the TOE and its development without incurring substantial reengineering costs.
EAL 4: Methodically designed, tested, and reviewed:
Requires both a low-level and a high-level design specification; requires that the interface specification be complete; requires an abstract model that explicitly defines security for the product; and requires an independent vulnerability analysis. It is applicable in those circumstances where developers or users require a moderate to high level of independently assured security in conventional commodity TOEs, and there is willingness to incur some additional security-specific engineering costs.
EAL 5: Semiformally designed and tested:
Provides an analysis that includes all of the implementation. Assurance is supplemented by a formal model and a semiformal presentation of the functional specification and high-level design and a semiformal demonstration of correspondence. The search for vulnerabilities must ensure resistance to penetration attackers with a moderate attack potential. Covert channel analysis and modular design are also required.
EAL 6: Semiformally verified design and tested:
Permits a developer to gain high assurance from application of specialized security engineering techniques in a rigorous development environment, and to produce a premium TOE for protecting high-value assets against significant risks. The independent search for vulnerabilities must ensure resistance to penetration attackers with a high attack potential.
EAL 7: Formally verified design and tested:
The formal model is supplemented by a formal presentation of the functional speci-fication and high-level design, showing correspondence. Evidence of developer "white box" testing of internals and complete independent confirmation of developer test results are required. Complexity of the design must be minimized.
The first four levels reflect various levels of commercial design practice. Only at the highest of these levels (EAL 4) is there a requirement for any source code analysis, and this analysis is required only for a portion of the code. The top three levels provide specific guidance for products developed using security specialists and security-specific design and engineering approaches.
National Institute of Standards and Technology
NIST has produced a large number of
Federal Information Processing Standards Publications
(FIPS PUBs) and special publications (SPs) that are enormously useful to security managers, designers, and implementers. Following are a few of the most significant and general. FIPS PUB 200 "Minimum Security Requirements for Federal Information and Information Systems," is a standard that specifies minimum security requirements in 17 security-related areas with regard to protecting the confidentiality, integrity, and availability of federal information systems and the information processed, stored, and transmitted by those systems.
NIST SP 800-100 "Information Security Handbook: A Guide for Managers," provides a broad overview of information security program elements to assist managers in understanding how to establish and implement an information security program . Its topical coverage overlaps considerably with ISO 17799.
Several other NIST publications are of general interest. SP 800-55 "Security Metrics Guide for Information Technology Systems," provides guidance on how an organization, through the use of metrics, identifies the adequacy of in-place security controls, policies, and procedures .
SP 800-27 "Engineering Principles for Information Technology Security (A Baseline for Achieving Security)," presents a list of system-level security principles to be considered in the design, development, and operation of an information system . SP 800-53 "Recommended Security Controls for Federal Information Systems," lists management, operational, and technical safeguards or countermeasures prescribed for an information system to protect the confidentiality, integrity, and availability of the system and its information .
Other Standards and Guidelines
Another important set of standards is the Control Objectives for Information and Related Technology (COBIT) , a business-oriented set of standards for guiding management in the sound use of information technology. It has been developed as a general standard for information technology security and control practices and includes a general framework for management, users, IS audit, and security practitioners. COBIT also has a process focus and a governance flavor; that is, management's need to control and measure IT is a focus point. COBIT was developed under the auspices of a professional organization, the
Information Systems Audit and Control Association, (ISACA). The documents are quite detailed and provide a practical basis for not only defining security requirements but also implementing them and verifying compliance.
Another excellent source of information is "The Standard of Good Practice for Information Security" from the Information Security Forum.
The standard is designed as an aid to organizations in understanding and applying best practices for information security. Because it addresses security from a business perspective, The Standard appropriately recognizes the intersection between organizational factors and security factors.
In addition to these standards, numerous informal guidelines are widely consulted by organizations in developing their own security policy. The
CERT Coordination Center (www.cert.org) has an Evaluations and Practices section of its Website with a variety of documents and training aids related to information security for organizations. The
Chief Information Officers Council (cio.gov) has published a collection of Best Practices and other documents related to organizational security.
 Eloff, J., and Eloff, M., "Information Security Management,"
Proceedings of SAICSIT 2003,
South African Institute of Computer Scientists and Information Technologists, 2003.
 International Organization for Standardization, "ISO/IEC 27001 – Information technology – Security Techniques – Information security management systems – Requirements," June 2005.
 Common Criteria Project Sponsoring Organisations, "Common Criteria for Information Technology Security Evaluation, Part 1: Introduction and General Model," CCIMB-2004-01-001, January 2004.
 Common Criteria Project Sponsoring Organisations, "Common Criteria for Information Technology Security Evaluation, Part 2: Security Functional Requirements," CCIMB-2004-01-002, January 2004.
 Common Criteria Project Sponsoring Organisations, "Common Criteria for Information Technology Security Evaluation, Part 3: Security Assurance Components," CCIMB-2006-09-003, September 2006.
 National Institute of Standards and Technology, "Minimum Security Requirements for Federal Information and Information Systems," FIPS PUB 200, March 2006.
 National Institute of Standards and Technology, "Information Security Handbook: A Guide for Managers," NIST Special Publication 800-100, October 2006.
 "Security Metrics Guide for Information Technology Systems," NIST Special Publication 800-55, July 2003.
 National Institute of Standards and Technology, "Engineering Principles for Information Technology Security (A Baseline for Achieving Security)," NIST Special Publication 800-27, June 2004.
 National Institute of Standards and Technology, "Recommended Security Controls for Federal Information Systems," NIST Special Publication 800-53, February 2005.
 IT Governance Institute, "COBIT 4.0.," USA, 2005.
 Information Security Forum, "The Standard of Good Practice for Information Security," 2005.
WILLIAM STALLINGS is a consultant, lecturer, and author of more than a dozen books on data communications and computer networking. His latest book, with Lawrie Brown, is
Computer Security: Principles and Practice
(Prentice Hall, 2007). He maintains a computer science resource site for computer science students and professionals at
and is on the editorial board of Cryptologia. He has a Ph.D. in computer science from M.I.T. He can be reached at