API Security Case Study | Financial Platform Security

The challenge

A financial platform had grown rapidly and its API layer had accumulated critical security gaps. The engineering team had prioritised feature velocity over security hardening - a common pattern that becomes acutely dangerous in financial services contexts where APIs handle sensitive account data, transaction processing, and customer PII.

🚨 No AI-driven threat detection. The security team had no proactive visibility into suspicious API behaviour patterns. Anomalies - unusual request volumes, credential stuffing attempts, data scraping patterns - were only discovered reactively, after damage had potentially occurred. The threat detection capability was entirely manual and rule-based.

🚨 Weak authentication and authorisation. APIs were protected by basic API key authentication with no token expiry, no scope restrictions, and no revocation mechanism. A compromised key provided unlimited access to the entire API surface until manually rotated - a process that took days due to coordination requirements.

🚨 Regulatory and compliance failure risk. The platform was approaching an audit period and the security team had identified that several financial regulation requirements - relating to access logging, data encryption in transit, and authentication strength - could not be demonstrated as met under the existing architecture.

🚨 No traffic controls or abuse protection. APIs had no rate limiting, no IP allowlisting for partner integrations, and no request validation. This left the platform exposed to enumeration attacks, scraping of sensitive financial data, and denial-of-service via API flooding - all without generating any alerts.

🚨 Unencrypted sensitive data in transit. Several internal service-to-service APIs were communicating over plain HTTP within the internal network. While external APIs used HTTPS, the assumption that internal networks are inherently trusted is considered a serious security anti-pattern - particularly for financial data.

Security architecture implemented

Multi-Layer API Security Framework

🛡️ OAuth 2.0 + JWT - Token-based authentication with scopes & expiry Auth

🤖 AI Anomaly Detection - Real-time suspicious activity classification AI / ML

🚦 API Gateway - Rate limiting, IP whitelisting, request validation Gateway

🔒 TLS Encryption - End-to-end for all internal & external APIs Encrypted

📋 Compliance Logging - Tamper-evident audit trail for every API call Compliant

🔍 Centralised SIEM Integration - All events aggregated and correlated Monitoring

Our solution

OKRUTI implemented a multi-layered API security framework - combining AI-based anomaly detection, industry-standard authentication protocols, traffic controls, and end-to-end encryption. Critically, every security control was also mapped to the relevant regulatory requirement, generating a compliance evidence matrix that could be handed directly to auditors.

→ AI-Powered Real-time Threat Detection: Deployed ML models that baseline normal API behaviour patterns per endpoint and per consumer. The system detects deviations - unusual request volumes, atypical access patterns, credential stuffing sequences, and data exfiltration signatures - and raises immediate alerts with severity classification. False positive rates were tuned down to less than 2% within the first month.

→ OAuth 2.0 + JWT Authentication: Replaced API key authentication with OAuth 2.0 authorisation flows and short-lived, scoped JWTs. Access tokens expire in 15 minutes; refresh tokens use rotation to prevent replay attacks. Scopes restrict each API consumer to the minimum permissions required, following the principle of least privilege across every integration.

→ API Gateway Security Controls: Deployed an API Gateway layer implementing per-consumer rate limiting (preventing flooding), partner IP allowlisting (restricting B2B APIs to known network ranges), payload size limits (preventing DoS via oversized requests), and schema validation (rejecting malformed requests before they reach application services).

→ End-to-end TLS Encryption: Applied mutual TLS (mTLS) for all service-to-service communication within the platform's internal network - eliminating the trust-the-internal-network assumption. External APIs use TLS 1.3 with HSTS headers. Certificate rotation is automated, removing the risk of expired certificate outages.

→ Compliance-Mapped Audit Logging: Implemented centralised, tamper-evident logging of all API activity - capturing request metadata, response codes, authentication context, and timing. Each log event is tagged with the regulatory requirement it satisfies, enabling automated compliance reporting ahead of audit periods with zero manual preparation effort.

Results achieved

Zero

Security breaches post-implementation - no unauthorised access incidents in the 12 months following deployment

100%

Regulatory compliance achieved - clean audit result with automated evidence matrix delivered to auditors

Proactive threat detection - anomaly detection catching suspicious patterns before any damage occurs

↑

Stakeholder and regulator trust - client passed regulatory review with zero findings on API security controls

"OKRUTI made our APIs secure, strong, and fully compliant with industry standards."

- Client, Financial Platform (sourced from okruti.com project page)

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