ISO/IEC 27001 formally specifies an Information Security Management System, a governance arrangement comprising a structured suite of activities with which to manage information risks (called ‘information security risks’ in the standard).
The ISMS is an overarching framework through which management identifies, evaluates and treats (addresses) the organisation’s information risks. The ISMS ensures that the security arrangements are fine-tuned to keep pace with changes to the security threats, vulnerabilities and business impacts - an important aspect in such a dynamic field, and a key advantage of ISO27k’s flexible risk-driven approach as compared to, say, PCI-DSS.
The standard covers all types of organizations (e.g. commercial enterprises, government agencies, non-profits) of all sizes (from micro-businesses to huge multinationals) in all industries (e.g. retail, banking, defense, healthcare, education and government). This is clearly a very wide brief.
ISO/IEC 27001 does not formally mandate specific information security controls since the controls that are required vary markedly across the wide range of organizations adopting the standard. The information security controls from ISO/IEC 27002 are summarised in annex A to ISO/IEC 27001, rather like a menu. Organizations adopting ISO/IEC 27001 are free to choose whichever specific information security controls are applicable to their particular information risks, drawing on those listed in the menu and potentially supplementing them with other a la carte options (sometimes known as extended control sets). As with ISO/IEC 27002, the key to selecting applicable controls is to undertake a comprehensive assessment of the organization’s information risks, which is one vital part of the ISMS.
Furthermore, management may elect to avoid, share or accept information risks rather than mitigate them through controls - a risk treatment decision within the risk management process.
ISO/IEC 27001 is derived from BS 7799 Part 2, first published as such by the British Standards Institute in 1999.
BS 7799 Part 2 was revised in 2002, explicitly incorporating the Deming-style Plan-Do-Check-Act cycle.
BS 7799 part 2 was adopted as the first edition of ISO/IEC 27001 in 2005 with various changes to reflect its new custodians.
The second edition of ISO/IEC 27001 was published in 2013, having been extensively revised to align with the other ISO management systems standards. PDCA is no longer explicit, but the concept of continuous refinement and systematic improvement remains, for sure.
Structure of the standard
ISO/IEC 27001:2013 has the following sections:
0 Introduction - the standard describes a process for systematically managing information risks.
1 Scope - it specifies generic ISMS requirements suitable for organizations of any type, size or nature.
2 Normative references - only ISO/IEC 27000 is considered absolutely essential to users of ’27001: the remaining ISO27k standards are optional.
3 Terms and definitions - see ISO/IEC 27000.
4 Context of the organization - understanding the organizational context, the needs and expectations of ‘interested parties’ and defining the scope of the ISMS. Section 4.4 states very plainly that “The organization shall establish, implement, maintain and continually improve” the ISMS.
5 Leadership - top management must demonstrate leadership and commitment to the ISMS, mandate policy, and assign information security roles, responsibilities and authorities.
6 Planning - outlines the process to identify, analyze and plan to treat information risks, and clarify the objectives of information security.
7 Support - adequate, competent resources must be assigned, awareness raised, documentation prepared and controlled.
8 Operation - a bit more detail about assessing and treating information risks, managing changes, and documenting things (partly so that they can be audited by the certification auditors).
9 Performance evaluation - monitor, measure, analyze and evaluate/audit/review the information security controls, processes and management system, systematically improving things where necessary.
10 Improvement - address the findings of audits and reviews (e.g. nonconformities and corrective actions), make continual refinements to the ISMS.
Annex A Reference control objectives and controls - little more in fact than a list of titles of the control sections in ISO/IEC 27002. The annex is ‘normative’, implying that certified organizations are expected to use it, but the main body says they are free to deviate from or supplement it in order to address their particular information risks. Annex A alone is hard to interpret. Please refer to ISO/IEC 27002 for more useful detail on the controls, including implementation guidance.