What is ISO/IEC 27001?

ISO/IEC 27001 is an international standard on how to manage information security. The standard was originally published jointly by the International Organization for Standardization (ISO) and the International Electrotechnical Commission (IEC) in 2005 and then revised in 2013. It details requirements for establishing, implementing, maintaining and continually improving an information security management system (ISMS) – the aim of which is to help organizations make the information assets they hold more secure. A European update of the standard was published in 2017. Organizations that meet the standard's requirements can choose to be certified by an accredited certification body following successful completion of an audit. The effectiveness of the ISO/IEC 27001 certification process and the overall standard has been addressed in a recent large-scale study.

How the standard works
Most organizations have a number of information security controls. However, without an information security management system (ISMS), controls tend to be somewhat disorganized and disjointed, having been implemented often as point solutions to specific situations or simply as a matter of convention. Security controls in operation typically address certain aspects of information technology (IT) or data security specifically; leaving non-IT information assets (such as paperwork and proprietary knowledge) less protected on the whole. Moreover, business continuity planning and physical security may be managed quite independently of IT or information security while Human Resources practices may make little reference to the need to define and assign information security roles and responsibilities throughout the organization.

ISO/IEC 27001 requires that management:

Systematically examine the organization's information security risks, taking account of the threats, vulnerabilities, and impacts;
Design and implement a coherent and comprehensive suite of information security controls and/or other forms of risk treatment (such as risk avoidance or risk transfer) to address those risks that are deemed unacceptable; and
Adopt an overarching management process to ensure that the information security controls continue to meet the organization's information security needs on an ongoing basis.
What controls will be tested as part of certification to ISO/IEC 27001 is dependent on the certification auditor. This can include any controls that the organisation has deemed to be within the scope of the ISMS and this testing can be to any depth or extent as assessed by the auditor as needed to test that the control has been implemented and is operating effectively.

Management determines the scope of the ISMS for certification purposes and may limit it to, say, a single business unit or location. The ISO/IEC 27001 certificate does not necessarily mean the remainder of the organization, outside the scoped area, has an adequate approach to information security management.

Other standards in the ISO/IEC 27000 family of standards provide additional guidance on certain aspects of designing, implementing and operating an ISMS, for example on information security risk management (ISO/IEC 27005).

Source: https://en.wikipedia.org/wiki/ISO/IEC_27001