API Compliance and Security: Meeting Modern Regulatory Expectations

APIs have become one of the fastest-growing attack surfaces. According to the Indusface State of Application Security – H1 2025 Report, API-targeted attacks surged by 104% year-over-year, highlighting the urgent need for stronger API protection.

As APIs power microservices, mobile apps, and third-party integrations, they now form a key part of the security perimeter. Compliance frameworks like PCI DSS v4.0, NIST SP 800-53, GDPR, SOC 2, and ISO 27001 have also begun explicitly addressing API security within their requirements.

For security leaders, this marks a clear shift. API security is no longer optional; it is a compliance necessity and cornerstone of digital trust.

Key Compliance Standards with API-Security Implications

Here are the major standards you must consider with their API-relevant clauses and how they apply.

PCI DSS v4.0 / v4.0.1

The PCI DSS v4.0 (Payment Card Industry Data Security Standard) explicitly recognizes that APIs form part of custom/bespoke code and thus must be treated in scope. For example:

• Requirement 6.2.3: Review of custom application code (including APIs and libraries) before release to identify and remove vulnerabilities.
• Requirement 6.3.2: Maintains inventory of bespoke and custom software, which explicitly includes APIs.
• Requirement 8.6.3: Addresses non-human user credentials (service accounts, API keys) and mandates rotation/management.

There are further expansions in v4.0.1 indicating a push to treat APIs similarly to web-apps and moving from static compliance to “continuous” security.

If your organization processes, stores or transmits cardholder data and uses APIs (internal or external) as part of the payment flow; you must treat those APIs under PCI scope, meaning secure by design, controlled, monitored, and audited just like other systems.

NIST Frameworks (including CSF 2.0, SP 800-228)

The NIST Cybersecurity Framework 2.0 and related publications such as NIST SP 800‑228 (“Guidelines for API Protection for Cloud-Native Systems”) provide a structured way to manage API security as part of your overall risk and compliance program.

For example:

• SP 800-228 emphasizes the identification of risk factors in APIs during development and runtime and sets out “basic and advanced controls” for API protection.
• NIST CSF 2.0’s six core functions (Govern, Identify, Protect, Detect, Respond, Recover) can be directly applied to API security.

Even if you don’t fall under PCI or other sector-specific regulation, aligning to NIST gives you a control-framework approach that helps you build audit-ready evidence, manage API risk systematically, and integrate API security into your broader enterprise risk management.

ISO/IEC 27001 & Other Frameworks

While not always API-specific, standards such as ISO/IEC 27001 (Information Security Management System) include controls that apply to APIs: asset & configuration management, access control, cryptography, vulnerability management, and incident response. These controls implicitly cover APIs because they are part of your information systems.

If your organization is certified (or going for certification) under ISO 27001, you must ensure your API layer meets the expected controls especially around inventory, access, monitoring, change management and secure development.

General Data Protection Regulation (GDPR) – Europe

Article 5(1)(f) requires that personal data be “processed in a manner that ensures appropriate security of the personal data, including protection against unauthorized or unlawful processing and against accidental loss, destruction or damage”.

Article 32 states that you must implement “appropriate technical and organizational measures” to ensure confidentiality, integrity, availability and resilience of processing systems, which would include APIs.

From an API perspective, you must first classify your APIs based on the type of personal data they handle. Once high-risk and sensitive endpoints are identified, ensure they enforce strong authentication, encryption, minimal data exposure, and continuous logging and monitoring.

The requirement is risk-based: what “appropriate security” means depends on the risk, data type, volume, context.

Payment Services Directive 2 (PSD2) / Open Banking frameworks

For financial services in the EU, PSD2 mandates that APIs used for account information services (AIS) and payment initiation services (PIS) must support strong customer authentication (SCA) and secure communication.

Example: APIs must allow third-party providers (TPPs) to access account and transaction data securely and reliably; the API must be equivalent in availability and performance to direct bank interfaces.

The UK’s Open Banking Limited standard states that read/write APIs must implement multi-layer security (OAuth2, OpenID Connect, mTLS) for API authentication/authorization

Cloud / Service-Provider Standards: ISO/IEC 27017 & ISO/IEC 27018

ISO 27017 (cloud-service provider security) adds cloud-specific controls (including API-based services) built upon ISO 27001.

If your APIs operate in a cloud service model (SaaS, PaaS, etc.), you may also need to consider ISO 27017/27018 (privacy in cloud) where APIs become part of the service stack.

While not “API security only” standards, they require you to include API endpoints in your access-control, encryption, vendor management, and audit logging frameworks.

How API Security Strengthen Compliance Readiness

Here is a more detailed walkthrough of what you should do to ensure APIs are secure, auditable, and compliant.

1. Build API security into the SDLC (Shift-Left + Shield-Right)

From the design phase through to production, you must embed API security. That means starting threat modelling of your API endpoints, defining the API specification (OpenAPI/Swagger), designing for least-privilege access, versioning and deprecation policies. After production, you must maintain runtime protections, monitoring and vulnerability scanning.

PCI 6.2.3 (pre-release review of custom/bespoke code including APIs) requires that you build security into API code. Also, NIST SP 800-228 emphasizes pre-runtime and runtime controls.

Implementation Tips

• Require developers to provide API specs which include security scheme definitions (authentication, authorization).
• Use automated scanning tools (SAST, DAST) for API endpoints.
• Include APIs in secure-coding training (for developers and DevOps), especially emphasize API-specific risks (e.g., BOLA – Broken Object Level Authorization).
• Use a version-management policy: mark older versions as deprecated, monitor use, retire when unsupported.

AppTrana’s API DAST scanner identifies vulnerabilities in APIs before production release, ensuring compliance with PCI’s pre-release testing requirements. Its continuous runtime protection blocks exploits at the edge while feeding findings back into DevSecOps pipelines, supporting the Shift-Left + Shield-Right approach.

2. API Discovery & Inventory – Know your attack surface

Often APIs proliferate internally (“shadow APIs”) or remain undocumented. You need an up-to-date inventory of all APIs (internal, external, partner, legacy) including metadata: owner, data classification, version, exposed audience, risk ranking.

PCI 6.3.2 explicitly requires maintenance of an inventory of bespoke/third-party software including APIs. NIST SP 800-228 mentions identifying risk factors during various activities of the API life-cycle.

Implementation Tips

• Deploy tools (automated discovery) to scan your environment and detect API endpoints, including undocumented ones.
• Tag each API with risk attributes: e.g., “public-facing”, “internal only”, “exposes PII”, “payment data”.
• Incorporate inventory updates into change-management: when new API is built or deployed, add to inventory.
• Review inventory periodically (monthly or quarterly) to capture drift or newly exposed APIs.

AppTrana automatically discovers APIs exposed to the internet, mapping endpoints, HTTP methods, and response patterns. These are continuously scanned and classified by risk severity, helping maintain an up-to-date inventory aligned with PCI and NIST requirements. The AppTrana dashboard offers ownership tagging, versioning visibility, and integration with change-management workflows to maintain ongoing inventory accuracy, aligning API compliance.

3. Authentication, Authorization & Access Control

APIs must enforce strong identity/authentication mechanisms (OAuth 2.0, OpenID Connect, mTLS, API key management) and enforce fine-grained authorization (object-level access, least privilege). This covers human users, machine users (service accounts), and third-party integrations.

Implementation Tips

• For each API endpoint determine “who should call it” and “what it can return”. Enforce authorization at object-level (not just endpoint-level).
• For machine/third-party integrations, create service‐accounts with unique credentials, monitor usage, enforce credential rotation at defined intervals.
• Use MFA or step-up authentication for sensitive API operations (e.g., financial transactions).
• Implement secure credential management: avoid hard-coded keys, embed secrets in vaults, rotate regularly.

4. Encryption, Transport Security & Data Protection

To meet API compliance, ensure all API communications use TLS/HTTPS (no unsecured HTTP), disable weak cipher suites, enforce encryption at rest for sensitive data, apply data-minimization (only return what is needed). For APIs handling payment-card or PII data, this is vital.

Implementation Tips

• Enforce TLS 1.2+ (or TLS 1.3) for all endpoints. Disable SSL/TLS versions below 1.2.
• Ensure API certificate management: monitor expiry, renew, avoid self-signed in production.
• For responses, apply logic to avoid excessive data exposure, e.g., an API should not return full user profile unless needed; use field-level filtering.
• For data at rest (e.g., logs, databases storing API responses) use encryption and key-management appropriately.

AppTrana enforces TLS 1.3+ for all API traffic, preventing downgrade attacks or weak cipher use. Built-in data leak protection inspects outbound responses to block exposure of PII or card data.

5. Rate Limiting, Throttling & Abuse Protection

APIs are vulnerable to misuse: scraping, brute-force, credential stuffing, and DDoS. Implement rate limiting and throttling per API consumer, IP or user-account. Monitor for unusual patterns.

Implementation Tips

• Set baseline request-limits per consumer and enforce hard/soft limits.
• For suspicious behavior (e.g., high-error rate, repeated invalid credentials) apply escalation controls (immediate throttling, captchas, token invalidation).
• Monitor for “burst” traffic or unusual endpoint usage, integrate with SIEM to generate alerts.
• Combine with bot-mitigation capabilities for public/exposed APIs.

AI-powered AppTrana applies adaptive rate limiting and behavioral analysis to prevent brute-force, scraping, and DDoS attacks against APIs. Its managed bot mitigation engine classifies requests by intent using a Bot Score, ensuring legitimate traffic continuity while blocking automated abuse, addressing runtime protection and availability controls.

6. Monitoring, Logging, Threat Detection & Incident Response

You must log API calls (who, when, what endpoint, what response code), monitor in near-real-time for anomalies, retain logs for forensic readiness, and have an incident response plan specific for API compromise or misuse.

Implementation Tips

• Ensure logs capture API caller identity, endpoint, timestamp, payload size, response code.
• Use anomaly-detection tools (based on baseline behavior) to catch unusual patterns (e.g., machine calls later at odd hours, endpoint returns unexpectedly high data volume).
• Define an API-incident-response playbook: what to do if an API is abused, data exfiltrated, or large-scale calls are detected.
• Retain logs for a defined period (e.g., 1 year) to support audit and forensic investigations.

AppTrana delivers comprehensive traffic logging and threat visibility, capturing full API transaction metadata for compliance audits. Logs can be exported to SIEM tools for correlation, and the managed SOC team provides 24×7 monitoring and incident response support. Every API security event is mapped to the API compliance control that it satisfies, enabling audit-ready reporting. The logs are retained for one-year while most other tools give access to weekly logs.

7. Vulnerability Management & Testing

Regularly perform API-specific vulnerability scanning (OWASP API Top 10 risks), penetration testing of API endpoints (including business-logic tests), patch/upgrade API components, deprecate old API versions.

How to achieve

• Use dynamic API-scanners that understand REST/GraphQL endpoints.
• Conduct manual business-logic pentests: e.g., can user A access user B’s data via API?
• Maintain version-tracking for APIs; retire unsupported versions promptly.
• Document remediation, track open findings, link to your inventory and risk-ranking.

According to the Indusface State of Application Security – H1 2025 Report, vulnerability attacks on APIs surged 13X year-over-year, highlighting the need for immediate remediation.

With AppTrana’s SwyftComply, open vulnerabilities are autonomously patched at the edge, ensuring compliance continuity and eliminating exposure windows between detection and remediation.

8. Governance, Risk Management & Documentation

You need to embed API security and compliance into your governance framework: define roles, responsibilities, policies, risk-criteria, control objectives, audit-evidence requirements.

How to achieve

• Define API-security policy: e.g., “All APIs must have authentication, rate-limiting, logging, inventory entry.”
• Assign ownership: each API must have an owner responsible for security, versioning and deprecation.
• Use risk-based ranking of APIs: e.g., high risk = public-facing + handles PII + partner integration; moderate risk = internal APIs; low risk = sandbox/test APIs.
• Maintain audit-evidence: API inventory logs, version-change logs, security-scan results, remediation records, incident logs

API Standards Are Compliance Accelerators

While compliance frameworks such as PCI DSS, HIPAA, and GDPR define what organizations must protect, API-specific standards like OWASP API Security Top 10 define how to achieve that protection.
By aligning regulatory clauses with these technical standards, enterprises can translate API compliance language into measurable engineering practices.

For a deeper dive into key API standards, protocols, and their security implications, explore our detailed guide API Security Standards and Protocols: A Primer

By being deliberate, risk-based and tool-enabled, you will be able to treat API security as a cornerstone of both your security and compliance strategy, not just a checkbox.

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