SDN centralizes control, which centralizes risk. The controller becomes a high-value target.
Controller security: Restrict management access, use strong authentication and MFA, encrypt controller-to-switch communication, log all API calls, keep software patched.
Attack surfaces:
Northbound API. Authenticate all requests.
Southbound interface. Mutual TLS authentication.
Cluster traffic. Encrypt east-west communication.
SDN security benefits: Rapid threat response, dynamic quarantine, centralized policy, better visibility.
SDN can improve security if you protect the controller properly.