Third-party relationships can extend an organisation’s reach, improve efficiency and support growth. They can also create routes into systems, data and operations that are difficult to monitor directly.
Recent research highlights the scale of the supply chain security challenge facing UK organisations. Risk Ledger’s Every Link Matters: The State of Supply Chain Security 2026 – UK Edition found that 82.4% of UK organisations experienced at least one supply chain cyber security incident in the past year, while 47.2% suffered repeat compromises. Combined with evidence of limited visibility into supplier cyber risk, these findings point to a persistent gap between the importance of supply chain security and how effectively it is managed in practice.
The challenge is not to eliminate every third-party risk. It is to understand where exposure exists, detect suspicious activity quickly and recover effectively when a supplier or service provider is compromised.
This guide explains how organisations can strengthen their approach to supply chain security. It examines the changing threat landscape, the regulatory considerations that require verification and the role that Managed Extended Detection and Response (MXDR) can play in improving visibility across connected environments.
A supply chain attack uses a trusted relationship, supplier connection or shared technology component to compromise another organisation. Rather than attacking every target directly, threat actors may compromise a service provider, software supplier, managed service provider or widely used application.
This approach can give an attacker access to multiple organisations through one successful intrusion. The resulting impact depends on the supplier’s access, the systems involved and how quickly the compromise is identified and contained.
Supply chain attacks can take several forms, including:
The common factor is trust. Suppliers often have legitimate access to systems and data, which means their activity can appear normal until an attacker misuses that access.
Traditional supplier assessments often rely on annual questionnaires, contract reviews and point-in-time audits. These activities can provide useful information, but they do not show how a supplier’s risk changes between assessments.
A supplier may change its technology, subcontractors, administrative accounts or security controls during the year. An account that was appropriately secured during an assessment may later be exposed through credential theft, excessive permissions or poor access management.
The complexity increases when an organisation relies on several layers of suppliers. A direct supplier may use its own service providers, cloud platforms or software dependencies. This creates a wider ecosystem in which the organisation may have limited contractual control or technical visibility.
A practical third-party risk programme should therefore consider:
This approach moves the discussion from whether a supplier has completed a questionnaire to whether the organisation can identify and manage the exposure created by that relationship.
UK cyber security regulation is evolving, with proposed and existing requirements placing greater emphasis on governance, incident management, resilience and supply chain oversight. The exact obligations depend on the legislation, the organisation’s sector, its size and whether it falls within a defined category of regulated entity.
Organisations should verify the current position through official government and regulatory sources before using specific reporting deadlines, penalties or scope statements in external communications.
Even where a particular requirement does not apply directly, the underlying expectations are relevant. Boards and senior leaders increasingly need evidence that the organisation understands its important dependencies, has proportionate controls in place and can respond when a supplier is affected.
A credible programme should be able to demonstrate:
Compliance should support better risk management rather than become a substitute for it. A completed assessment does not prove that a supplier is secure, and regulatory alignment does not remove the need for effective detection and response.
Continuous monitoring can help organisations identify suspicious activity that periodic supplier assessments cannot detect. Managed Extended Detection and Response combines technology, monitoring and security expertise to analyse signals across relevant parts of the environment.
The value of MXDR depends on the quality and coverage of the underlying data. Where appropriate, this may include signals from:
Microsoft Security capabilities can provide a foundation for bringing these signals together. Microsoft Sentinel can help centralise security data and support investigation across multiple sources. Microsoft Defender capabilities can contribute endpoint, identity, email and cloud signals where the relevant products are deployed and correctly configured.
The practical outcome is improved visibility of activity that may otherwise be treated as isolated events. For example, an unusual sign-in by a supplier account may become more significant when considered alongside new privilege assignments, unfamiliar device activity or access to sensitive resources.
Technology does not replace supplier governance. It should support it by helping security teams:
The effectiveness of these controls depends on implementation, data quality, integration coverage and the organisation’s operating model. Managed services can provide additional capacity where internal teams do not have the resources to monitor and investigate activity around the clock.
Identity is a central control point in supplier security. Third-party users should receive only the access required for their role, and that access should be reviewed as responsibilities change.
Microsoft Entra ID can support controls such as multifactor authentication, conditional access and privileged identity management, subject to licensing, configuration and the organisation’s operating requirements.
A proportionate access model should consider:
These controls reduce the potential impact of a compromised account. They do not remove the risk entirely, particularly where a supplier has broad administrative privileges or where access is difficult to attribute to an individual.
Supplier relationships often involve the exchange of personal data, intellectual property, financial information or operational records. Security teams should understand where that information is stored, how it is accessed and how it is protected after it leaves the organisation’s direct control.
Microsoft Purview may support data classification, information protection, data loss prevention and governance activities where the relevant capabilities are licensed and configured for the organisation’s needs.
The appropriate controls will depend on the information involved and the supplier relationship. They may include:
The objective is not to create a claim of complete control over every supplier environment. It is to reduce unnecessary exposure and create clearer accountability for sensitive information.
A mature programme combines supplier governance with technical controls and tested response arrangements. It should be proportionate to the importance of the relationship rather than applying the same process to every supplier.
Start by identifying suppliers that support important services, process sensitive data or have privileged access to the environment. Consider the impact of disruption, compromise or supplier failure.
Useful categories may include:
This prioritisation helps direct assurance and monitoring resources towards the relationships that could cause the greatest harm.
Supplier questionnaires, certifications and audits can provide useful assurance, but they should form part of a wider control framework.
Organisations should combine them with:
The aim is to identify material changes in risk rather than simply repeat the same assessment each year.
Contracts and operating procedures should define what happens when a supplier experiences a security incident. Responsibilities should cover detection, escalation, communication, investigation, containment, recovery and evidence preservation.
An effective plan should answer:
These arrangements should be tested. A written plan that has never been exercised may not work when teams are dealing with incomplete information and operational pressure.
A maturity-based framework can help organisations move from isolated checks to a measurable improvement programme. Possible areas of assessment include:
The measures should demonstrate progress in reducing exposure and improving response capability. Counting completed questionnaires alone does not provide a reliable view of resilience.
Organisations looking to improve supply chain security can begin with five practical actions:
CyberOne can support organisations that need to assess third-party risk, improve Microsoft Security controls or extend their monitoring capability through managed services. The appropriate starting point should depend on the organisation’s current maturity, risk profile and operating model.
The goal is not to create the appearance of control. It is to develop a clear and measurable ability to understand exposure, respond to incidents and maintain important operations when a supplier is affected.