Conduct a security review of every third-party vendor you depend on

A security review of every third-party vendor you depend on extends vendor agreement review discussed elsewhere into genuine, active security assessment — your own security posture is only as strong as the weakest link across your complete vendor ecosystem, since a security failure at any vendor with access to your data or systems can create genuine risk regardless of how solid your own direct practices are.

This review should genuinely assess each significant vendor's actual security practices — what certifications or security standards they maintain, their own incident response and breach notification practices, how they handle the specific data or access you've granted them, and their overall security maturity relative to the sensitivity of what you're entrusting to them.

The genuine depth of this review should reasonably scale with each vendor's actual access and the sensitivity of what they handle — a vendor with access to genuinely sensitive customer data warrants more thorough security evaluation than a vendor providing a more limited, lower-risk service, making risk-proportionate review depth a practical approach to this potentially extensive undertaking.

This represents an area where genuine, systematic evaluation, rather than simply trusting vendor marketing claims about their security practices, provides real protective value — requesting actual security documentation, certifications, or even conducting more formal security assessments for your most significant, highest-access vendors closes off risk that would otherwise remain unexamined and potentially significant.