Why do third-party vendors and connected systems increase cyber risk in financial services?

Why This Matters for Security Teams

Third-party connections are a force multiplier for financial services risk because they turn one institution’s control problem into a shared trust problem. Vendors often touch payment flows, customer data, trading platforms, support tooling, and back-office workflows, so a weakness in their environment can become an entry point into high-value systems. The practical issue is not just whether a supplier is “secure enough,” but whether its access is tightly scoped, monitored, and revocable when conditions change. The 2024 ESG Report: Managing Non-Human Identities shows how common that exposure has become, including broad compromise rates and extensive third-party exposure of non-human identities, which helps explain why vendor access now features so heavily in incident reviews. Financial firms that treat every connected system as equally trustworthy usually discover the opposite only after an unexpected path is abused.

How It Works in Practice

Vendor risk usually accumulates through a few repeatable mechanics: overbroad access, weak credential discipline, poor telemetry, and unclear ownership of the connection. A supplier may start with a narrow integration and gradually gain more permissions as business teams add features or tolerate exceptions. Over time, those exceptions create standing access that attackers can abuse if the vendor is compromised, if its support channel is hijacked, or if an integration token is exposed. In financial services, the main control challenge is to reduce trust without breaking business-critical connectivity. That means classifying each third-party relationship by what it can reach, how it authenticates, how often it is reviewed, and who can revoke it quickly. A useful way to think about this is:

• limit vendor access to the minimum systems and data required for the task;
• separate production access from test, support, and analytics access;
• require strong authentication and short-lived credentials where feasible;
• log and review vendor actions, not just login events;
• treat integrations, API keys, and service accounts as governed assets, not background plumbing.

This is why supply-chain controls and identity controls overlap in practice. OWASP Non-Human Identity Top 10 is useful here because many vendor connections operate through API keys, service accounts, and other machine-to-machine trust relationships that need explicit lifecycle management. In financial environments, EU Digital Operational Resilience Act (DORA) reinforces the expectation that third-party ICT risk must be understood, governed, and tested, not simply documented. These controls tend to break down when business owners treat vendor access as a one-time onboarding task and never revalidate what the connection can still do.

Common Variations and Edge Cases

Tighter vendor control often increases operational friction, so organisations have to balance resilience against speed, supportability, and regulatory pressure. Not every third-party relationship carries the same risk: a low-impact SaaS tool does not warrant the same scrutiny as a provider with access to payment processing, customer data, or privileged administrative functions. Current guidance suggests focusing first on blast radius, not on vendor labels. The hardest edge cases are managed service providers, outsourced operations, embedded fintech partners, and shared platforms where multiple institutions rely on the same integration layer. In those models, the real risk is concentration: one compromise can affect many downstream systems at once. Another common failure mode is “temporary” access that becomes permanent because no one owns the cleanup. Financial firms also need to distinguish between business continuity access and day-to-day access, because emergency support paths often become the easiest way in. Ultimate Guide to NHIs, Key Challenges and Risks is a useful reference when a vendor relationship depends on long-lived machine credentials, since those assets frequently outlive the original business justification. The 2024 ESG Report: Managing Non-Human Identities also helps frame why third-party exposure becomes so persistent when machine identities are not tightly governed. The edge case to watch is any relationship where the vendor can act faster than the institution can detect and revoke, because that is where shared trust turns into shared exposure.

Risk and Threat Considerations

Third-party and connected-system risk is fundamentally about expanded attack paths and reduced assurance. A vendor compromise can give an attacker a legitimate path into financial systems, which is often harder to detect than direct intrusion because the traffic may look like normal partner activity. Failure mechanism: The common abuse pattern is credential theft, token reuse, excessive privilege, or compromise of a supplier’s own environment, followed by lateral movement through trusted integrations or support access. If the connection uses standing credentials or broad permissions, the attacker inherits that trust and can reach data or operational systems without needing to defeat the institution’s front door. Impact: The result can be data exposure, fraudulent transactions, service disruption, regulatory scrutiny, and a much wider containment problem because the institution must investigate both its own estate and the vendor relationship that enabled access.

Practitioner Guidance

What to prioritise: Start with the third-party connections that can reach production, customer data, payments, or administrative functions. Those are the relationships where a small access mistake creates the largest blast radius.

What to verify: Confirm that each vendor connection has a named owner, a current business purpose, scoped permissions, and a reliable revocation path. If no one can answer who can disable it today, the control is weaker than the documentation suggests.

Decision rule: If a vendor needs persistent access, treat it as a high-risk exception and require stronger monitoring, shorter credential lifetimes, and explicit periodic review. If the access is intermittent, prefer just-in-time or event-based access instead of standing trust.

Practitioner takeaway: The real question is not whether a vendor is trusted, but whether the institution can bound, observe, and remove that trust before it becomes an attacker’s shortcut.

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