Multi-tenant infrastructure is a shared computing environment where one platform serves multiple customers at the same time. Common examples include hosting platforms, cloud control planes, SaaS applications, and managed databases. Each customer should be logically separated, but the underlying hardware, software, and administration layers are often shared.
It matters in cyber security because a weakness in one tenant, control panel, identity system, or backup service can expose other tenants through the same shared stack. Attackers may target an admin portal, abuse a privileged account, or steal data from one customer and use it to pivot, disrupt service, or apply extortion pressure against the provider and its users. Defenders reduce risk with strong tenant isolation, least-privilege access, MFA, logging, segmentation, patching, and regular testing of administrative paths and backup restore procedures.