Case Study 3: A Financial Services API Security Success

A major financial services firm (anonymized for confidentiality) provides an excellent example of threat modeling preventing a potentially catastrophic breach. The organization was developing a new open banking API platform to comply with PSD2 regulations while enabling fintech partnerships.

The threat modeling exercise began during initial architecture discussions. The team used STRIDE methodology enhanced with financial industry-specific threats. They identified several critical threats that weren't immediately obvious: race conditions in transaction processing that could enable double-spending, JWT implementation flaws that might allow token forging, and API composition attacks where combining legitimate API calls could bypass business logic.

One particularly interesting finding involved their OAuth implementation. The threat model revealed that their planned implementation would be vulnerable to authorization code injection attacks. By identifying this during design, they implemented PKCE (Proof Key for Code Exchange) and additional validation, preventing a vulnerability that had affected other financial institutions.

The threat model also identified risks in their API rate limiting strategy. Initial designs used simple per-API rate limits, but threat modeling revealed how attackers could circumvent these by distributing calls across multiple endpoints. This led to implementing global rate limiting with intelligent pattern detection, preventing various abuse scenarios.

Six months after launch, automated attack tools targeted the platform with techniques that exactly matched scenarios identified in the threat model. The implemented controls successfully prevented all attacks. The organization credits threat modeling with preventing potential losses in the millions and maintaining customer trust in their digital transformation.