Third-party risk in cyber security: a growing challenge for UK businesses

Modern businesses rely on an intricate web of third-party providers, vendors and digital supply chain partners. These third-party relationships are essential for efficiency and growth, but they also increase your exposure to cyber threats.

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In the UK, third-party cyber threats and supply chain attacks are a growing concern. According to the Cyber Security Breaches Survey 2025, over 43% of businesses reported experiencing a cyber security breach in the past year, and many rely on suppliers and external IT services that can introduce additional risk. The question for every organisation is not if, but when a vulnerability in a third-party relationship could impact business operations.

Why third-party risk management matters in the UK

In highly regulated sectors like financial services, healthcare and retail, a vendor’s security posture directly impacts your resilience. If critical suppliers are compromised, the risk to your organisation is immediate and severe.

Despite this, the Cyber Security Breaches Survey 2025 found that only 14% of businesses formally reviewed the risks posed by their immediate suppliers, and just 7% looked at their wider supply chain. Even among larger firms, fewer than half carried out structured supplier risk reviews.

This gap shows that while cyber attacks are common, very few organisations actively assess how their vendors and partners could expose them to threats.

Let’s be clear – the risks are not theoretical. In recent months, the UK has seen high-profile supply chain incidents, including a third-party contractor breach which affected Marks & Spencer, causing operational disruption, financial loss, and reputational harm to the retailer. This incident alone demonstrates that third-party cyber risk is not a distant, strategic concern but an operational reality.

The most common third-party cyber risks

1. Supply chain attacks

Attackers exploit digital supply chains to compromise trusted software or hardware. These third-party attacks bypass traditional defences because they come from authorised vendors. Continuous monitoring tools and strong incident response planning are critical to reduce exposure.

2. Weak vendor security practices

A vendor’s security posture can make or break your defences. Poor patching, insecure cloud setups, and outdated systems create potential risks that affect your data security. Risk management teams must evaluate vendor assessment results carefully to identify inherent risk and ensure proper security practices.

3. Excessive vendor access

Third-party providers often require system access to deliver services. Without strict access controls, this can escalate into a security breach. Limiting access to third-party assets and using continuous monitoring reduces the risk posed by compromised credentials.

4. Human exploitation and phishing

Many cyber attacks begin with phishing emails sent via a third-party vendor relationship. Once attackers compromise a vendor, they impersonate them to launch social engineering attacks. Educating security teams and employees is essential in managing cyber risks effectively.

5. Regulatory and compliance failures

When a vendor mishandles sensitive data, your business remains legally responsible under UK GDPR and the Data Protection Act 2018. Compliance risk is heightened if third-party data breaches are not detected, reported, and managed quickly.

The impact of third-party data breaches

Third-party threats can lead to more than data loss. They can cause:

• Operational disruptions that delay business operations.

• Financial instability due to fines, recovery costs and lost revenue.

• Reputational damage with customers losing confidence in your ability to protect sensitive data.

• Compliance penalties from regulators if reporting deadlines are missed.

Ultimately, your ability to manage third-party risk determines how well your organisation can maintain business continuity during security incidents.

Building a risk reduction strategy

Effective third-party risk management combines proactive assessments with strong incident response. Here are key elements of a risk reduction strategy:

1. Vendor Risk Assessment
   Begin with a structured risk assessment process. Identify critical vendors, assess inherent risk, and evaluate each vendor’s security posture.

2. Continuous Monitoring
   Use continuous monitoring tools and security ratings to track third-party threats in real time. This ensures your organisation stays aware of evolving cyber risks.

3. Clear Data Handling Procedures
   Establish policies for how third parties manage sensitive data. Ensure that their security program aligns with your own security controls and practices.

4. Incident Response Planning
   Build vendor-specific incident response planning into contracts. This ensures that when a data breach occurs, your risk management teams and the vendor can act quickly to mitigate risks.

5. Ongoing Risk Assessments
   Managing risks is not a one-time exercise. Ongoing monitoring, regular risk assessments and vendor reassessments are essential for long-term protection.

Final thoughts

Third-party cyber risk is one of the most significant security challenges facing UK businesses today. From supply chain attacks to vendor security failures, the risks are real and rising. But with effective vendor risk management, continuous monitoring and robust incident response planning, businesses can reduce exposure and protect sensitive data.

Zensec believes that cyber security should not be about fear. It should be about enabling businesses to thrive securely, even in the face of evolving cyber threats. With the right risk reduction strategy and trusted partners, your organisation can face the digital future with confidence.

How Zensec helps manage third-party risk

At Zensec, we provide more than incident response, we provide peace of mind. Our services include:

• 24x7x365 digital forensic and incident response to contain breaches quickly.

• Support for insurers and international loss adjustors, ensuring financial recovery aligns with incident response.

• Vendor risk management expertise, guiding businesses through due diligence, vendor assessment and ongoing monitoring.

• Risk reduction strategies, tailored to mitigate risks, maintain business continuity and improve your organisation’s security posture.

We partner with security teams, risk management teams and compliance officers to provide clarity and control in the face of uncertainty.