Multi-Factor Authentication protects accounts by requiring more than one factor to log in. But MFA systems rarely run in isolation. Most rely on sub-processors: third-party providers that handle SMS delivery, push notifications, voice calls, cryptographic keys, or device management. Each sub-processor is another link in the chain. If one breaks, the whole chain is compromised.
Identifying and managing MFA sub-processors is not optional. Every integration, every outsourced function adds scope to your threat surface. Attackers know sub-processors are often less monitored. A compromised SMS gateway can intercept codes. A vulnerable push notification API can be hijacked. Even metadata leaks from a secondary provider can give attackers enough to target your users.
To control this risk, maintain a full inventory of all sub-processors used in your MFA workflow. Map their role: token generation, out-of-band delivery, recovery channel, or verification algorithms. Audit them against compliance requirements like GDPR or SOC 2. Confirm they use secure transport, enforce strong authentication internally, and provide timely incident disclosure. Require contracts that mandate security, uptime, and breach notification.