Supply chain is the network of suppliers, software developers, service providers, components, and processes used to build and deliver an organization’s products or services. In a security threat model, it extends the trust boundary beyond the organization: a compromised supplier account, build system, software dependency, update mechanism, or hardware component can introduce malicious code, expose credentials, or undermine systems used by many customers.
Effective protection starts with mapping critical suppliers, dependencies, data flows, and access, then applying risk-based due diligence and least-privilege, segmented access. For software, maintain an inventory such as a software bill of materials, verify signed artifacts and update provenance where feasible, and monitor dependencies for vulnerabilities or unexpected changes. Contracts and technical controls should support timely notification and investigation. Response plans should cover revoking supplier access, isolating affected versions or integrations, determining exposure, and coordinating remediation with the provider.