How to conduct a third-party risk assessment: a practical guide

Organisations rely on an increasing number of third parties to support critical business operations. Whether it’s a cloud provider, software vendor, managed service provider or specialist supplier, these external relationships can deliver significant value. They can also introduce cyber security risks, compliance risks, operational risks and financial risks that sit outside your direct control.

As supply chains become more interconnected and cyber threats continue to evolve, understanding and managing third party risks has become a critical part of any effective third party risk management (TPRM) programme.

A third-party risk assessment helps organisations evaluate vendor risk, identify potential risks and ensure suppliers meet the security, compliance and operational standards required to support the business safely.

In this guide, we’ll look at how to conduct a third-party risk assessment and the key areas every organisation should evaluate.

If you are reading this because your organisation has experienced a cyber incident and is unsure how to respond, contact Zensec immediately.

What is a third-party risk assessment?

A third-party risk assessment is a structured process used to evaluate the risks associated with third party vendors, suppliers and external partners.

The aim is to understand how a vendor’s activities, security posture and business practices could impact your organisation. This includes assessing cyber security risks, regulatory compliance, data protection practices, financial stability and operational resilience.

A thorough third party risk assessment provides organisations with the information needed to make informed decisions about vendor relationships and implement appropriate risk mitigation measures where necessary.

Importantly, third-party risk assessments should not be viewed as a one-off exercise. Effective vendor risk management requires ongoing monitoring throughout the lifecycle of the relationship.

Why third-party risk assessments matter

Many organisations now depend on dozens, or even hundreds, of third-party vendors to support day-to-day operations. These suppliers often have access to sensitive data, critical systems and valuable company assets.

This creates new opportunities for attackers.

Recent third party breaches and supply chain attacks have highlighted the risks associated with trusted vendors. A security weakness within a single supplier can potentially expose multiple organisations to data breaches, regulatory penalties and operational disruption.

Beyond cyber security, organisations must also consider compliance risks, financial risks and reputational risks. If a vendor fails to meet regulatory requirements or experiences a significant outage, the impact can quickly affect customers, stakeholders and business operations.

This is why third party risk management has become a key component of broader risk management strategies.

Build a risk-based assessment process

Not all third parties present the same level of risk. Assessing every supplier against the same criteria can be inefficient and resource-intensive.

A better approach is to adopt a risk-based framework that prioritises vendors according to the level of risk they introduce.

Start by identifying which suppliers:

• Have access to sensitive data
• Connect to internal systems
• Support critical business operations
• Handle customer information
• Provide essential services the organisation depends upon

These suppliers often require more detailed reviews than lower-risk vendors with limited access or business impact.

Understanding your organisation’s risk appetite also helps determine what level of risk is considered acceptable and which vendors require additional controls.

Identify critical vendors and high-risk vendors

One of the first steps in any third-party risk assessment is identifying critical vendors and high risk vendors within your vendor ecosystem.

A supplier hosting customer data will typically present a different risk profile to a company providing office supplies. Similarly, a managed service provider with administrative access to systems will generally require a more detailed assessment than a marketing supplier with limited access.

By classifying vendors according to their risk profiles, organisations can focus time and resources where they are most needed.

This risk-based approach is a core principle of effective vendor risk management and helps security teams prioritise their efforts.

Evaluate key risk areas

A comprehensive supplier risk assessment should examine several areas of risk rather than focusing solely on cyber security.

Cyber security risks and security controls

Cyber security risks are often a primary focus of third-party risk management because vendors frequently have access to critical systems and sensitive data.

When conducting a vendor risk assessment, organisations should review the supplier’s security controls and overall security posture. This may include evaluating:

• Access controls and authentication methods
• Vulnerability management processes
• Security monitoring capabilities
• Incident response plans
• Data encryption practices
• Security awareness programmes

Understanding a vendor’s risk posture provides valuable insight into their ability to defend against cyber threats and respond effectively to security incidents.

Regulatory compliance and data protection

Organisations remain responsible for protecting customer data, even when that data is processed or stored by third parties.

A third-party risk assessment should evaluate whether suppliers meet relevant compliance requirements and industry regulations. This may include GDPR obligations, sector-specific standards and internal governance requirements.

Assessing data protection controls helps reduce compliance risks and demonstrates due diligence when working with external partners.

Operational and financial risks

Operational failures can have just as much impact as cyber security incidents.

Consider whether a supplier supports critical services, how dependent the organisation is on that vendor and what would happen if the service became unavailable. Business continuity arrangements, resilience planning and recovery capabilities should all form part of the assessment.

Financial risks should also be considered. A supplier experiencing financial difficulties may struggle to maintain service quality, invest in security or meet contractual commitments. Evaluating financial stability helps identify potential risks before they become larger business issues.

Conduct vendor due diligence

Due diligence is a crucial stage of the risk management process.

Many organisations use vendor risk assessment questionnaires to gather information about a supplier’s policies, security controls and governance practices. These questionnaires can provide a useful starting point, particularly when assessing large numbers of vendors.

However, questionnaires alone rarely provide a complete picture.

Where possible, organisations should validate responses by reviewing supporting evidence such as certifications, audit reports, security policies and independent assessments. This helps ensure that assessment decisions are based on evidence rather than assumptions.

For high-risk vendors and critical vendors, additional scrutiny is often appropriate.

Assign risk scores and prioritise action

Once assessment information has been collected, organisations need a consistent way to evaluate results.

Risk scores help quantify vendor risk and make it easier to compare suppliers across the organisation. They can also help identify critical risks that require immediate attention.

Common factors used when assigning risk scores include:

• Likelihood of a security incident
• Potential business impact
• Access to sensitive data
• Compliance obligations
• Strength of existing security controls

The objective is not to eliminate all risk. Instead, organisations should focus on ensuring risk levels remain within acceptable limits and implementing risk mitigation measures where necessary.

A structured scoring approach also helps support reporting and decision-making across internal and external stakeholders.

Establish continuous monitoring

One of the most common mistakes organisations make is treating a third-party risk assessment as a one-time activity.

Risk changes over time.

A supplier’s security posture may deteriorate, regulatory requirements may change or new vulnerabilities may emerge. Without ongoing monitoring, these issues can go unnoticed until they result in a significant problem.

Effective third party risk management should therefore include continuous monitoring throughout the vendor lifecycle.

This may involve monitoring:

• Security incidents
• Data breaches
• Emerging threats
• Regulatory developments
• Vendor performance
• Changes in risk profiles

Continuous monitoring tools can help organisations collect risk data and identify issues earlier, enabling security teams to respond before risks escalate.

By establishing ongoing monitoring processes, organisations gain greater visibility into third party risks and can make more informed decisions regarding supplier relationships.

Engage the right stakeholders

Third-party risk management is not solely the responsibility of the security team.

Effective assessments require input from procurement teams, compliance specialists, legal advisers, operational stakeholders and business leaders. Each group provides a different perspective on risk and helps ensure assessments are aligned with business objectives.

Collaboration between internal and external stakeholders also improves accountability and supports more effective management of third party relationships.

A well-defined governance structure is often one of the key factors that separates mature TPRM programmes from less effective approaches.

Common mistakes to avoid

Even organisations with established party risk management programmes can encounter challenges.

Some of the most common mistakes include:

• Assessing all vendors in exactly the same way
• Relying solely on vendor risk assessment questionnaires
• Failing to establish ongoing monitoring
• Ignoring operational and financial risks
• Overlooking changes in a vendor’s risk posture
• Treating assessments as a compliance exercise rather than a risk management activity

Avoiding these pitfalls can significantly improve the effectiveness of vendor risk management efforts.

Conclusion

A third-party risk assessment is one of the most effective tools for identifying and managing the risks associated with vendors, suppliers and external partners.

By evaluating cyber security risks, compliance requirements, operational resilience and financial stability, organisations can gain a clearer understanding of vendor risk and take steps to mitigate risks before they impact the business.

Effective third party risk management goes beyond initial risk assessments. Through due diligence, structured risk scoring and continuous monitoring, organisations can manage vendor risks more effectively, protect sensitive data and build greater resilience across their supply chain.

As third party relationships continue to expand, organisations that adopt a proactive approach to assessing and managing third party risks will be better positioned to reduce exposure, maintain regulatory compliance and strengthen overall security.