Technical Due Diligence for SaaS Vendors

SaaS vendors process your data on their infrastructure, making technical due diligence uniquely important. You cannot inspect their servers directly, so you must evaluate their architecture, security practices, and operational maturity through structured inquiry and evidence review. For executives approving SaaS procurement, understanding what to ask—and what the answers mean—can prevent costly mistakes.

Critical Technical Areas to Evaluate

SaaS due diligence goes beyond checking for certifications. Your team should investigate the vendor’s technical architecture and operational security in depth:

• Data architecture — is your data logically or physically isolated from other tenants? Where is it stored geographically? Can you choose data residency?
• Encryption — what algorithms are used for data at rest (AES-256 minimum) and in transit (TLS 1.2+)? Who manages the encryption keys? Can you bring your own keys (BYOK)?
• Authentication and access — does the vendor support SSO via SAML/OIDC, enforce MFA, and provide granular role-based access controls?
• API security — how are APIs authenticated? Is rate limiting enforced? Are APIs regularly tested for vulnerabilities?
• Infrastructure security — which cloud provider hosts the service? What redundancy and failover mechanisms are in place? How are patches and updates managed?
• Logging and monitoring — does the vendor provide audit logs accessible to customers? How long are logs retained? Are security events monitored in real time?

Red Flags and Deal-Breakers

Certain findings during technical due diligence should raise immediate concern. Shared encryption keys across tenants, lack of MFA support, inability to provide audit logs, and refusal to disclose the underlying cloud provider are serious red flags. Similarly, vendors that cannot articulate their patching cadence or have no documented incident-response plan present unacceptable risk for sensitive workloads.

Consider engaging your security team to conduct a lightweight penetration test or vulnerability scan of the vendor’s externally facing infrastructure, subject to contractual permission. External scanning tools can reveal exposed services, outdated software, and certificate issues that the vendor may not have disclosed.

Action Steps

1. Develop a standardised SaaS technical due-diligence template covering all six evaluation domains
2. Require vendors to provide architecture documentation and data-flow diagrams before contract signing
3. Mandate SSO integration and MFA support as non-negotiable requirements for all SaaS vendors
4. Include the right to conduct external vulnerability scanning in your vendor contracts