When a payroll provider was breached last year, thousands of employers felt the impact. Paychecks were delayed, employee data exposed, and HR teams scrambled to respond. None of those organizations were directly attacked, but they all paid the price.
That’s the reality of third-party cyber risk: you can do everything right and still face disruption from someone else’s vulnerability.
The third-party ripple effect.
Every connection strengthens your business and expands your risk. Whether it’s a vendor, cloud provider, or contractor, your third-party network is part of your cybersecurity story. You can’t control every partner’s defenses, but you’re still accountable when something goes wrong.
As organizations rely on more external partners than ever, third-party cyber risk has become one of today’s most urgent business threats. Here’s how these relationships can expose your organization, and how to stay protected.
Understanding third-party cyber risk.
Modern organizations operate within complex networks of vendors, suppliers, and technology partners, often called the “cyber supply chain.” While these relationships power efficiency and innovation, they also expand your exposure. A single vendor can trigger a domino effect across your customers, and reputation.
It’s simple: your cyber security is only as strong as your weakest link.
Even with robust internal controls, a gap in a vendor’s defenses can open the door to costly disruptions. Vendor risk management is no longer options, it’s an essential component of a resilient cybersecurity strategy.
Where risk hides.
System Integration
- Connected systems, connected vulnerabilities: API integrations and cloud connections streamline workflows but can also create direct pathways between networks. Limit access to only what’s necessary.
- Privileged access: Vendors don’t always need admin rights. Apply the principle of least privilege to reduce exposure.
- Network connections: VPNs and direct connections may expand reach, and your attack surface. Consider segmented or time-bound access instead.
The Trusted Insider Program
Once a vendor has access, monitoring their behavior isn’t always easy. Know exactly which vendors can access which systems, and review this often. When partnerships end, make sure access ends too. Dormant accounts are open doors for attackers.
Data Sharing
- Sensitive data exposure: Vendors may need financial, customer, or proprietary data, but challenge every data request. Only share what’s necessary.
- Legal implications: If your vendor experiences a breach, you may still be liable. Review notification requirements and confirm responsibilities before an incident occurs.
The cost of complacency.
In 2025, insider attacks carried the highest average breach cost at $4.92 million — but third-party and supply chain breaches were right behind at $4.91 million, proving how costly external vulnerabilities can be. These breaches are a clear reminder that organizations need to take vendor risk seriously. The financial hit from third-party incidents is nearly the same as the cost of the most damaging internal attacks.
When a third-party vendor experiences a cyber breach, the financial impact on the affected organization can be wide-ranging and severe. The costs typically fall into five key categories:
- Remediation and recovery: Expenses tied to incident response, forensic investigations, and restoring compromised systems.
- Business disruption: Downtime, lost productivity, and supply chain delays, often reaching hundreds of thousands of dollars per hour.
- Legal and regulatory: Fines, lawsuits, and compliance-related reporting requirements.
- Reputational damage: Customer loss, brand erosion, and costly public relations efforts.
- Direct financial losses: Fraud, ransom payments, or stolen assets.
Due Diligence.
Companies that take vendor reviews and data-sharing agreements seriously build trust with clients, carriers, and regulators alike.
Today’s cyber insurers are also paying attention, often asking for proof that vendor management practices are in place and that your team knows what to look for.
Doing your due diligence isn’t about checking boxes. It’s about asking the right questions before risk lands on your doorstep.
Key Security Areas to Evaluate
Mitigating third-party risk.
Third-party relationships are inevitable, what matters is understanding the risks and taking steps to protect your organization. Here’s how to strengthen your defenses.
Before the partnership
- Evaluate security posture: review a vendor’s cybersecurity policies, incident history, and certifications.
- Review the contract: Confirm insurance coverage, align on incident response plans, and ensure mutual indemnification. Limit system access to what’s truly necessary.
During the partnership
- Maintain visibility: Keep a current inventory of all vendors, including what systems they can access and what data they handle.
- Review regularly: Perform annual or quarterly security reviews. Risk levels change, so should your oversight.
- Leverage technology: Continuous monitoring tools and vendor risk management platforms can help flag issues early and assess partners’ cyber hygiene in real time.
Third-party partnerships are unavoidable, but unmanaged risk isn’t. Do your due diligence before signing on, limit access to what’s necessary, and review vendor connections regularly. The principle of least privilege isn’t just good IT hygiene, it’s good business. In the end, visibility and vigilance are your strongest defenses against third-party cyber risk.
Yes/And: Our Take
Yes, partnering with vendors drives innovation and efficiency, and it also requires intention and oversight. At M3, we help organizations look beyond the surface of their vendor relationships, evaluating where risks may hide, strengthening contracts, and aligning cybersecurity practices with insurance strategy.
Need to review your vendor risk strategy? Connect with your M3 Client Executive and keep your partnerships powering growth, not risk.
