Concentrated dependency is a risk pattern in which many systems, organizations, or business processes depend on the same provider, platform, or control layer. That layer may be a cloud region, DNS service, identity provider, payment gateway, managed security tool, or network backbone. The danger is not only that the shared component can fail, but that one failure can affect many unrelated services at once.
In cyber security, this matters because it increases the blast radius of both outages and attacks. A compromise, misconfiguration, power loss, or control-plane error in a shared dependency can block logins, break name resolution, interrupt updates, or take critical applications offline. Defenders reduce the risk by mapping upstream dependencies, adding redundancy across regions and vendors, testing failover and restore procedures, using immutable backups where appropriate, and reviewing contracts for incident response and exit options. The goal is resilience: no single control layer should be able to stop the entire service chain.