PCI DSS, or the Payment Card Industry Data Security Standard, is a global security standard designed to protect payment account data. It applies to organisations that store, process or transmit cardholder data, as well as entities that can affect the security of the cardholder data environment. 

 Organisations that store, process or transmit payment card data may be required to comply with PCI DSS. This can include merchants, service providers, financial institutions and technology providers. The exact validation requirements depend on factors such as the organisation's role, transaction volumes and the requirements of the relevant acquiring bank or payment brand. 

 PCI DSS v4.0.1 is the current version of the PCI Data Security Standard. It includes requirements covering areas such as authentication, access control, vulnerability management, monitoring, security testing, e-commerce security and targeted risk analysis. 

 The requirements that apply depend on your payment environment, how cardholder data is handled and the systems, people and processes that can affect its security. A PCI DSS scoping exercise can help identify the cardholder data environment and determine which systems and controls fall within scope. 

 A Qualified Security Assessor, or QSA, is a security professional qualified through the PCI Security Standards Council to assess organisations against PCI DSS requirements. QSAs can support scoping, gap analysis, remediation planning and formal PCI DSS assessments. 

 A PCI DSS Scope Analysis identifies where payment account data is stored, processed or transmitted and determines which systems, networks, people and processes fall within the cardholder data environment. Accurate scoping can help reduce unnecessary compliance complexity and ensure relevant controls are properly assessed. 

 A PCI DSS Gap Assessment compares an organisation's current security controls against applicable PCI DSS requirements. It identifies areas of non-compliance and provides recommendations to help prioritise remediation before a formal assessment or self-assessment is completed. 

 A formal PCI DSS assessment evaluates whether an organisation meets the applicable requirements of the standard. Depending on the organisation and its validation requirements, this may involve a Qualified Security Assessor completing a Report on Compliance or an eligible organisation completing a Self-Assessment Questionnaire. 

 A Report on Compliance, or ROC, is a detailed assessment report used to document an organisation's compliance with PCI DSS. It is typically completed by a Qualified Security Assessor where an assessor-led validation is required. 

 An Attestation of Compliance, or AOC, is an official PCI SSC form used to confirm the result of a PCI DSS assessment. The appropriate AOC depends on the type of assessment completed, such as a Report on Compliance or Self-Assessment Questionnaire. 

 PCI DSS compliance is generally validated on a recurring basis, but the exact frequency and assessment method depend on the organisation and requirements set by the relevant acquiring bank, payment brand or other compliance-accepting entity. Some security activities, such as vulnerability scanning, may also need to be performed more frequently. 

 If gaps are identified during an assessment, the organisation will normally need to remediate the relevant issues before compliance can be validated. The actions required will depend on the findings, the assessment type and any requirements set by the organisation's acquiring bank or payment brand.