Financial services firms should treat third parties as part of their attack surface, not outside it. Start by limiting shared data to the minimum needed, enforcing multi factor authentication, and verifying that vendors have visible security controls and sound cyber hygiene. Where data is stored or transferred, access should be tightly scoped, monitored, and reviewed regularly to prevent exposure through weak links in the chain.
Why third-party data sharing becomes a supply chain problem
Once a financial services firm shares regulated, customer, or operational data with a vendor, the security boundary extends beyond its own environment. The practical issue is no longer only whether your controls are strong, but whether the other party can store, process, transmit, and return that data without creating exposure through weak authentication, overbroad access, or poor segregation.
That is why third-party risk in this setting is really a combination of confidentiality, access, and operational dependency risk. The firm still owns the data risk, even if a partner is the one hosting the system or handling the workflow.
Vendor exposure is especially material when the third party has persistent access, reusable credentials, or broad integration privileges. A weaker partner can become the path by which data is copied, misrouted, or retained longer than intended.
What controls actually reduce exposure in shared-data arrangements
The most effective controls are the ones that shrink the blast radius of the relationship. Data minimisation matters first: share only what the vendor needs for the specific use case, and separate production, testing, and support datasets whenever possible. That reduces the chance that a partner compromise turns into broad downstream exposure.
Authentication and access discipline matter just as much. Strong MFA, scoped access, and regular entitlement review help prevent inherited trust from becoming standing access. In practice, access should be limited to named business functions, time-bounded where possible, and revoked as soon as the vendor no longer needs it.
Security assurance should also be visible, not assumed. Firms need to know whether the vendor logs access, monitors for anomalous activity, rotates secrets, and keeps data isolated from other customers. For financial services firms, that visibility is often what separates a manageable third-party dependency from a silent concentration risk. SOC 2 Trust Services Criteria (AICPA) can help structure that assurance conversation where vendor trust evidence is required. EU Digital Operational Resilience Act (DORA) is also relevant for firms that need to govern ICT third-party risk with stronger operational resilience expectations.
How firms should manage the vendor relationship over time
Reducing supply chain risk is not a one-time onboarding exercise. It requires periodic review of the actual data flows, the permissions granted, and the controls the vendor still has in place. If the relationship changes, for example a new integration, a subcontractor, or a data location change, the risk profile changes too.
Good practice is to treat shared-data vendors as part of the ongoing control environment. That means revisiting the business justification for the sharing, checking whether the same outcome can be achieved with less data, and confirming that offboarding is clean when the relationship ends. If credentials, API keys, or support channels remain active after the contract ends, the firm has not really reduced supply chain risk, it has merely postponed it.
For firms that depend on cloud or software providers, NIST SSDF (SP 800-218) and SLSA are useful references for integrity and provenance thinking, while CSA Cloud Controls Matrix provides a broader vendor and cloud control mapping lens. When the relationship involves regulated financial workflows, those references help teams move from generic vendor trust to evidence-based control validation.
Risk and Threat Considerations
Shared data creates a path for compromise that often bypasses the firm’s own perimeter. The main risks are overexposure, weak third-party authentication, poor logging, and unmanaged reuse of vendor access, all of which can turn a routine integration into a source of breach propagation.
Failure mechanism: A vendor with broader-than-needed access, weak secret handling, or poor segregation can expose shared data through compromise, misuse, or accidental leakage, and that exposure may spread back into the firm’s own environment or other connected partners.
Impact: Sensitive client data, transaction data, or operational records can be disclosed, altered, or retained outside policy, creating regulatory, contractual, and reputational harm, plus longer recovery because the firm must investigate both its own systems and the vendor chain.
Standards & Framework Alignment
This section maps relevant standards and security frameworks to the operational risks and controls described in this guidance.
NIST CSF 2.0, NIST SP 800-53 Rev 5 and CSA Cloud Controls Matrix set the technical controls, while DORA and SOC 2 (AICPA) define the regulatory obligations.
| Framework | Control / Reference | Relevance |
|---|---|---|
| DORA | ICT third-party risk management | Financial firms need structured third-party resilience for shared-data vendors. |
| Recommendation — Govern ICT third-party risk with contractual, monitoring, and resilience controls. | ||
| SOC 2 (AICPA) | CC6.1 — Logical Access Security Software Controls | Vendor access and shared data depend on strong logical access safeguards. |
| CC7.2 — Change Management | Vendor integrations and access paths change over time and must be controlled. | |
| Recommendation — Require logical access controls for any vendor handling shared data. Review vendor access and data-flow changes before they go live. | ||
| NIST CSF 2.0 | GV.SC-01 — Third-Party Cybersecurity Risk Management Strategy | Shared-data vendors are a third-party risk governance problem. |
| PR.AA-01 — Identity Management, Authentication, and Access Control | MFA and scoped access are central to reducing vendor exposure. | |
| Recommendation — Define and enforce a third-party risk strategy for shared-data relationships. Apply strong authentication and least-privilege access to vendor accounts. | ||
| NIST SP 800-53 Rev 5 | AC-6 — Least Privilege | Vendor access should be scoped to the minimum required data and actions. |
| AC-20 — Use of External Systems | Shared-data arrangements rely on controlled use of external systems and services. | |
| Recommendation — Limit third-party permissions to the minimum necessary for the business use case. Control how external systems are allowed to access firm data. | ||
| CSA Cloud Controls Matrix | IAM — Identity and Access Management | Shared-data vendors need tightly scoped access and authentication controls. |
| SEF — Security Incident Management, eDiscovery, and Cloud Forensics | Vendor compromise requires visibility and response readiness across the chain. | |
| Recommendation — Apply IAM controls to vendor identities and shared access paths. Ensure vendor incident response and forensic visibility are contractually defined. | ||
Practitioner Guidance
What to prioritise: Start with the highest-value data and the vendor paths that can reach it. If a supplier can access production data, customer records, or reusable secrets, that relationship deserves immediate scoping, logging, and review before lower-risk integrations.
What to verify: Confirm that access is truly minimal, MFA is enforced, secrets are rotated, and offboarding actually removes access. The question is not whether the vendor has a policy, but whether the access path can still be used after the business need ends.
Practitioner takeaway: The best supply chain risk reduction comes from limiting what leaves the firm, limiting who can reach it, and making every third-party access path observable and revocable.
Related resources from NHI Mgmt Group
- How should security teams reduce supply chain risk when third-party integrations hold delegated access to critical SaaS data?
- How should security teams reduce supply chain risk from state-sponsored attacks through third parties?
- How should managed service providers reduce supply chain risk from third-party vendors and tools?
- How should FinTech teams reduce cyber risk when they share data with banks and other financial institutions?
Deepen Your Knowledge
Reviewed and updated by the NHIMG editorial team on September 25, 2026.
NHI Mgmt Group — the #1 independent authority on Non-Human Identity, IAM, and Agentic AI security. nhimg.org
