REST API Security Best Practices (2026): Complete Guide to Protecting Modern APIs

RESTful APIs have become the top attack surface for modern enterprises. They now process more than 90% of global web traffic, which makes them a direct gateway to backend systems and sensitive data. 

As usage has surged, so has interest from attackers. Gartner confirms that APIs are now the number one application attack vector, and recent research shows that 99% of organizations experienced an API security incident in the past year. 

Threat actors increasingly rely on credential abuse using stolen API keys or tokens, injection attacks against unsanitized inputs, malicious bots, which now account for nearly a third of API attacks, and the exploitation of shadow or forgotten endpoints that remain exposed without monitoring.

This landscape has made strong API security a business requirement. Enterprises must implement end-to-end security controls that cover the entire SDLC to reduce risk. These controls prevent data leakage, maintain uptime, support compliance, and avoid the high financial impact of breaches. 

Studies show that finding vulnerabilities pre-production through proactive API security testing creates significantly better outcomes for all: security teams, compliance goals, developer velocity, Security posture, incident prevention. 

In this context, platforms like Levo.ai bring significant value by unifying API discovery, testing, and runtime protection into a single, high precision API security platform. 

TL;DR

RESTful APIs have become the top attack surface in 2025. They now process more than 90% of all web traffic, and attackers know that APIs connect directly to backend systems and sensitive data. 

Gartner continues to report that APIs are the leading application attack vector, and recent research shows that 99% of enterprises experienced an API security incident in the past year. Credential abuse dominates these incidents, with 95% of attacks coming from authenticated sessions, followed by injection flaws, excessive data exposure that leaks PII, malicious bots responsible for roughly 30% of API attacks, and the growing problem of shadow endpoints that escape visibility.

Effective API security mandates full-spectrum coverage and automation: from cataloguing, documentation and pre-production security testing as shift-left best practices to continuous monitoring, threat-detection and blocking in production. 

When these pillars work together, enterprises reduce breach risk, maintain uptime, improve compliance readiness, and avoid the high cost of post incident remediation. Strong API security also protects customer trust and strengthens resilience in API driven ecosystems.

Levo.ai supports this effort by combining all of the above into a single unified platform that discovers, governs and protects APIs throughout the entire API lifecycle.

What Is REST API Security? Fundamentals, Controls & How REST APIs Work

A REST API is a web service that follows the architectural principles introduced by Roy Fielding in 2000 to make distributed systems scalable, predictable, and easy to maintain. REST stands for Representational State Transfer, which simply means that the client and server exchange representations of a resource’s state rather than entire objects. 

When a client requests information, it receives only the relevant details of the resource, usually in JSON or XML. The API then uses standard HTTP methods such as GET, POST, PUT, and DELETE to retrieve or modify these resource representations.

REST APIs are now the foundation of modern digital services. They power mobile apps, connect microservices inside large enterprises, and serve as the primary interface between customers and backend systems.

REST API security refers to the set of controls that safeguard these interfaces from unauthorized access, data exposure, and runtime abuse. Securing a REST API requires protecting every layer involved in its lifecycle: identity, input validation, business logic, data transport, and runtime behavior. Strong authentication and authorization are essential so that only verified clients can access resources and only within their permitted scope. Input data must be validated to prevent injection attacks or malformed requests from reaching backend systems. Sensitive information must be protected through encryption, strict data filtering, and careful handling of output responses.

In practice, securing a REST API involves applying several core measures:

1. Authentication and Authorization: Every request must be authenticated to identify the caller and authorized to verify that the caller has permission to perform the intended action. This includes API keys, OAuth tokens, JWTs, and role based or attribute based access checks. Consistent enforcement ensures that only legitimate clients can reach sensitive resources.

2. Input Validation and Output Filtering: All incoming data should be treated as untrusted. Validating inputs through schemas, whitelists, type checks, and length limits prevents issues such as SQL injection, NoSQL injection, and unsafe deserialization. Output filtering helps ensure the API does not expose unnecessary or sensitive fields.

3. Encryption: Transport encryption with HTTPS is essential to prevent interception or tampering. Sensitive fields inside payloads may require additional encryption or hashing. Server side storage of secrets, tokens, and passwords must follow strong cryptographic standards.

4. Rate Limiting and Throttling: APIs should restrict how frequently a client can make requests. This defends against brute force attempts, credential guessing, and denial of service conditions by preventing any single client from overwhelming the API.

1. Monitoring and Logging: A secure API implementation logs access attempts, authentication events, error patterns, and usage anomalies. Continuous monitoring helps detect abuse, bot activity, or suspicious behavior that may bypass preventive controls. Alerting and incident response workflows rely on this visibility.

Why REST API Security Matters in 2026: Rising Attacks, Breach Impact & Compliance Pressure

REST API security has become mission critical in 2026. APIs now sit at the center of digital operations, and attackers know it. The reasons API security matters more than ever can be understood through a few key drivers:

APIs Power Modern Digital Services

• Nearly ninety % of all web traffic now consists of API calls rather than traditional browser traffic.
• Mobile apps, cloud services, IoT devices, and partner ecosystems all depend on REST APIs.
• Any weakness in an API can disrupt entire workflows and expose sensitive data at scale.

Attack Volume and Sophistication Are Surging

• Gartner continues to identify APIs as the top application attack vector.
• Many enterprises have seen triple digit year over year growth in API attacks, including a three thousand % surge in some regions.
• Attackers now exploit API specific issues such as broken object level authorization, JSON based injections, and multi step workflows that traditional controls miss.
• Ninety nine % of enterprises reported at least one API security incident in the past year.

API Breaches Create High Impact Failures

• A single flawed API routinely exposes millions of records.
• API and bot attacks are responsible for more than eleven % of global cyber losses.
• Bot activity now accounts for roughly thirty % of API attacks, contributing to billions in annual business losses.
• Outages caused by insecure APIs force emergency shutdowns, disrupt customer services, and impact revenue.

Expanding Attack Surface from Mobile, IoT, and AI

• Mobile and IoT rely heavily on public facing APIs, often outside traditional perimeter controls.
• AI systems expose new API endpoints for model queries and data flows, creating fresh targets for exploitation.
• Incidents have already shown that flaws in AI or IoT APIs can be used to reach internal networks.

Rising Regulatory and Customer Expectations

• Data protection laws treat API access the same as web access, increasing audit pressure.
• Sectors such as finance, open banking, and healthcare now require stricter API level controls.
• Strong API security increasingly influences enterprise procurement, partner integration decisions, and customer trust.

APIs Are the Foundation of Future Innovation

• Microservices, event driven systems, partner integrations, and AI features all rely on stable and secure APIs.
• Industry leaders recognize API security as the foundation of modern application architecture, not an optional enhancement.
• Enterprises that mature their API security posture can innovate without increasing operational risk.

Common REST API Attack Vectors (Mapped to OWASP API Top 10)

Attackers focus heavily on REST APIs because they expose direct entry points to data and business logic. Many of the most common attack vectors map closely to the OWASP API Security Top 10. 

The following are the primary vectors attackers use in real incidents.

BOLA / IDOR: How Object-Level Authorization Failures Expose Sensitive Data

• Identified as the most widespread API vulnerability in the wild.
• Occurs when an API exposes object identifiers and fails to verify ownership or permissions.
• Attackers simply modify an ID in the request to access another user’s data.
• This vector has caused large scale data breaches through basic ID enumeration.
• Any endpoint that handles identifiers must enforce strict server side authorization.

Broken Authentication: Weak Tokens, Replay Attacks & Missing Auth Controls

• Targets weaknesses in how the API validates identity.
• Common issues include missing auth on sensitive endpoints, predictable API keys, token replay, and loose token validation.
• Nearly thirty % of surveyed API incidents involved broken authentication.
• Attackers who bypass auth gain full access to exposed backend functions.
• Strong and consistent token handling, session controls, and rate limits are essential.

Excessive Data Exposure: Overly Verbose Responses & Sensitive Data Leaks

• Occurs when APIs return more data than the client needs and depend on clients to hide fields.
• Attackers call the API directly and retrieve full payloads, including sensitive fields the UI never shows.
• Past breaches exposed password hashes, internal permissions, personal data, and private tokens due to overly verbose responses.
• APIs must follow the principle of least data and explicitly prune all sensitive fields server side.

Injection Attacks (SQL, NoSQL, OS, XXE) in REST APIs

• Attackers insert malicious input through JSON bodies, query parameters, or headers to manipulate downstream systems.
• SQL and NoSQL injection remain highly prevalent and have contributed to roughly one third of API security incidents along with BOLA.
• Automated fuzzing tools are commonly used to probe for injection points.
• Strong input validation, parameterized queries, and strict parsing rules are mandatory.

API DoS Attacks & Rate Abuse: Flooding, Resource Exhaustion & Bot Traffic

• APIs without rate limits can be overwhelmed by floods of requests or resource intensive queries.
• Attackers target endpoints that trigger expensive database operations or large responses to exhaust CPU or memory.
• Volumetric API abuse has caused outages and served as a diversion for other attacks.
• Throttling, payload size limits, and scalable infrastructure are required to counter these vectors.

Mass Assignment: How Attackers Abuse Implicit Field Mapping

• Occurs when backend frameworks automatically map JSON fields to internal objects.
• Attackers supply additional fields, such as role or price, to escalate privileges or manipulate internal state.
• This risk is now represented as Broken Object Property Level Authorization in the OWASP API Top Ten.
• Only explicitly allowed fields should be accepted, and all sensitive fields must be protected by server side authorization logic.

Business Logic Abuse: Workflow Manipulation & Multi-Step Attack Chains

• Exploits how the API is intended to work rather than exploiting a code flaw.
• Examples include skipping workflow steps, repeatedly applying promotions, or abusing order flows.
• Bots automate multi step logic abuse at scale, which significantly increases impact.
• Requires deep understanding of workflows, strong state validation, and anomaly detection to defend.

Security Misconfigurations: CORS, Debug Modes, Open Admin Routes & More

• Includes insecure defaults, weak CORS policies, debug modes, open admin consoles, misconfigured API gateways, and verbose error responses.
• These issues often result from deployment oversights rather than coding flaws.
• Misconfigurations remain a frequent cause of real world API incidents.
• Automated configuration scanning and strict deployment checklists are key safeguards.

Core Principles of REST API Security: Least Privilege, Zero Trust & Defense in Depth

Securing REST APIs requires more than individual controls. It rests on a set of foundational security principles that guide the design, development, and operation of APIs at scale. These principles ensure that security is consistent and resilient, even as architectures evolve and new threats emerge.

1. Least Privilege: Every client, user, or microservice interacting with an API should have only the minimum access required. This principle limits blast radius when credentials are stolen, which is significant given that 95% of API attacks in recent studies originated from authenticated sessions. Least privilege is enforced through granular roles and scopes, strict endpoint segmentation, and returning only the data the caller is entitled to view. Applied correctly, a compromised token provides a limited opportunity for misuse because the system never grants broad access by default.

2. Fail Securely: APIs must default to secure behaviors when errors or failures occur. If an authentication service is unavailable, the API denies access. If validation cannot parse the input, the request is rejected. Secure defaults prevent failures from creating unsafe states, which is critical for enterprise scale systems where small misconfigurations can expose large volumes of data. This principle also guides configuration: debug modes stay disabled, wildcard CORS is avoided, and sample accounts remain off.

3. Defense in Depth: No single control is sufficient. Attackers often chain weaknesses, such as combining a stolen token with a BOLA flaw to extract data across thousands of IDs. Defense in depth places multiple overlapping layers: authentication, authorization, input validation, output filtering, network segmentation, gateway policies, and monitoring. If one layer misses a threat, another can stop or detect it. This principle is especially important for stopping sophisticated multi step attacks that now dominate API threat reports.

4. Never Trust User Input: Treat all external input as malicious until validated. This includes JSON bodies, URL parameters, headers, file uploads, and XML payloads. Strong schema validation, pattern checks, type checks, and size limits prevent injections and deserialization attacks, which remain among the most exploited API vulnerabilities and contribute heavily to real world incidents. Validation must happen server side, not just at the gateway, and output encoding ensures that returned data does not introduce downstream risk.

5. Minimal Exposure: Expose only what is necessary. This principle applies to both data and functionality. APIs should avoid returning internal fields or verbose error messages that reveal system internals. Only required fields should appear in responses, mitigating excessive data exposure, a root cause of several major API breaches in which sensitive fields were present but hidden only by the user interface. Functionality should also be minimized; remove unused endpoints, disable unnecessary HTTP methods, and isolate admin functionality into dedicated internal APIs.

6. Continuous Monitoring and Improvement: Threats evolve, and APIs change frequently. Security must be constant. Runtime monitoring for anomalies, logging of key events, automated scanning in CI, periodic reviews of configurations, and regular pentests keep defenses current. Studies show that ninety nine % of enterprises experienced at least one API security incident in the past year, highlighting the need for constant oversight and rapid response. Continuous improvement ensures that vulnerabilities introduced through updates or architectural changes do not remain undetected.

‍Zero Trust: Zero Trust in API design means never assuming a request is legitimate, even if it originates from your internal network. Every call must authenticate and authorize independently. Internal services should present tokens or certificates on each request, and short lived credentials reduce the impact of stolen access. This principle limits lateral movement, which is a growing concern as enterprises rely heavily on microservices, partner APIs, and distributed workloads. Zero Trust forces verification across every boundary, strengthening overall resilience.

Common REST API Security Mistakes (and How to Avoid Them)

Even mature engineering teams routinely introduce API weaknesses through avoidable mistakes. These weaknesses are at the root of many real world API breaches and often create openings that attackers exploit long before development teams notice. 

Below are the most critical and frequent mistakes, with practical examples that show how they manifest in enterprise environments: 

1. Hardcoding Credentials: Teams sometimes embed API keys, OAuth tokens, passwords, or cloud credentials directly into source code or mobile binaries. Attackers regularly scan public repos and decompile mobile apps to find these secrets, and once a key is found, it often grants broad access. A typical example is a mobile app containing a hardcoded backend API key that effectively grants full read access to user data. The fix is straightforward: use secure secret stores, environment variables, and short lived tokens that can be rotated and monitored.

2. Keeping Deprecated or Unpatched APIs Online: Enterprises frequently replace an API with a new version while leaving older versions running indefinitely. These zombie APIs often rely on outdated libraries with known CVEs or older authentication schemes. Attackers specifically target them because they expose vulnerabilities long after the primary API has been hardened. An example is a v1 endpoint that lacks object level authorization even though v2 fixed the issue. A disciplined API lifecycle and deprecation schedule avoids this exposure.

3. Inconsistent or Weak Authentication: Many breaches begin with a single endpoint that “doesn’t need auth” or was intended only for internal use but ended up exposed. Health checks, test endpoints, and legacy integration points are common culprits. Attackers enumerate APIs for any unauthenticated path or any endpoint that accepts predictable API keys. Another common mistake is accepting expired or unsigned JWTs because token validation is misconfigured. The remediation involves enforcing a uniform authentication scheme across all endpoints and eliminating implicit trust throughout the stack.

4. Excessive Data Exposure and Verbose Errors: Developers often return entire database objects for convenience, leaving clients to hide sensitive fields. Attackers query the API directly and retrieve full payloads containing PII, internal flags, or even hashed credentials. Similarly, verbose errors can leak SQL statements, file paths, or stack traces that help attackers map the system. A safer approach is explicit field allow listing and generic error responses while logging the detailed diagnostic information internally.

5. Insufficient Logging and Monitoring: Many enterprises deploy APIs without comprehensive request logging or any automated review of suspicious patterns. This blind spot allows credential abuse, BOLA exploitation, and slow data exfiltration to go undetected for weeks or months. A typical scenario is an attacker iterating ID values and quietly harvesting data overnight because no anomaly detection or alerting is in place. Proper audit trails, real time alerts, and periodic log reviews are essential to detect misuse early and support incident response.

6. Shadow APIs and Untracked Third Party Endpoints: Teams often lack a complete inventory of their APIs. Shadow APIs emerge when developers publish endpoints outside formal review processes, when cloud configurations expose internal APIs unintentionally, or when acquired systems bring undocumented services online. Third party APIs can also introduce risk if their failures or breaches cascade into your environment. Continuous API discovery and strong governance help close these visibility gaps.

7. Misconfigured CORS or Client Side Assumptions: Many teams rely on CORS restrictions or client side logic for security, assuming that only their frontend will call an API. Attackers bypass both by sending direct requests. Misconfigurations, such as wildcard origins or allowed credentials, can allow malicious sites to trigger API calls from a user’s browser. APIs must be treated as public by default, and all enforcement must occur server side.

‍Poor API Versioning and Retirement Practices: Without strong versioning discipline, insecure legacy behavior stays online indefinitely. A classic example is an API that introduces stricter authorization in v2 but leaves v1 active to avoid breaking clients. Attackers simply continue targeting v1. Clear version timelines, communication to consumers, and automated retirement of deprecated endpoints prevent this long tail of risk.

REST API Security Best Practices (Enterprise-Ready Checklist)

A secure REST API requires consistent enforcement of proven controls rather than isolated fixes. The list below should help security leaders and engineering teams who need actionable guidance and enterprise ready standards: 

1. Authentication & Authorization

Require identity verification for every request, including internal APIs. Use OAuth 2.0 and OpenID Connect with short lived JWTs. Enforce server side validation for tokens and scopes. This reduces the risk of replay attacks or stolen long lived keys.

Authorization must be granular. Prevent object and function level access issues by verifying that the caller is allowed to access each specific resource. A common failure occurs when a user can retrieve another user’s record by simply changing an ID in the request. Enforce ownership checks on every sensitive route.

Example: A banking API prevented a major BOLA incident by enforcing a rule that accountId must match the authenticated user’s identity or assigned permissions, which stopped direct identifier manipulation during automated scans.

2. Validate & Sanitize All Input

Every input is untrusted, including headers and URLs. Validate incoming data using strict schemas and type checks. Use allow lists, boundary checks, and regular expressions for formats such as dates and email addresses.

Always use parameterized queries. Avoid string concatenation in SQL or NoSQL statements. Reject malformed JSON early to avoid parser exploits and disable XML external entities to prevent XXE attacks.

Example: A retail API blocked a wave of SQL injection attempts by validating all IDs as integers within a safe range before the query stage. The payloads never reached the database layer.

3. Enforce Strong Access Control Models

Apply role based or attribute based policies consistently. Protect every endpoint that performs privileged actions, including administrative or configuration operations.

A major source of breaches is assuming the UI will prevent dangerous actions. Attackers do not use the UI; they call the API directly. Validate permissions at the server for every operation.

Example: A SaaS provider avoided a cross tenant data access incident by requiring every query to include a tenant identifier that must match the authenticated tenant. The check was performed automatically through ORM filters.

4. Encrypt Everything

Use TLS for all traffic. Require TLS 1.2 or higher, and prioritize TLS 1.3. Never allow plaintext HTTP, even internally. Use mutual TLS for service to service calls when possible.

Encrypt sensitive data on disk. Use salted hashing for passwords and managed key vaults for API tokens and secrets.

Example: During a cloud misconfiguration incident, attackers accessed replicated storage. Encrypted records were unusable, preventing a high severity breach.

5. Follow the Principle of Minimal Exposure

Expose only what is necessary. Avoid returning entire objects from databases. Create dedicated response models that include only the required fields.

Use generic error messages in production. Verbose errors reveal stack traces, file paths, and internal logic.

Example: A health care API reduced its breach impact surface by moving from database object serialization to response DTOs, removing more than fifty internal fields that were previously leaking sensitive metadata.

6. Implement Robust Rate Limiting & Throttling

Limit how often a user, IP address, or key can call your API within a given time window. Apply stricter thresholds on login, token renewal, and other security critical endpoints.

This prevents brute force attacks, request floods, and scraping.

Example: A financial services API eliminated a credential stuffing campaign by reducing login attempts to a handful per minute, forcing attackers to abandon their automation.

7. Detect & Block Bots + Automated Abuse

Use behavior analysis, API keys, IP reputation feeds, and gateway level bot detection. Track client fingerprints and unusual call sequences.

Scrapers and bots often request resources in patterns no human user would generate.

Example: A gaming company blocked a large scale bot farm by identifying clients that performed thousands of item lookups in numerical order, something legitimate users never did.

8. Protect Against Injection & Payload Attacks

Parameterize all queries and use safe APIs for database access. Sanitize or encode outputs when your data may be rendered in a browser context.

Check file uploads for size, allowed types, and execution risks. Disable dangerous XML parser features.

Example: A marketplace API prevented a remote code execution incident by rejecting a polyglot file uploaded as an image that contained embedded script content.

9. Secure API Keys & Secrets

Never store secrets in source code, mobile apps, or client side JavaScript. Use secret managers and rotate keys regularly.

Restrict each key to the minimum required permissions and monitor its usage for anomalies.

Example: A startup avoided an expensive cloud breach when its secret management system flagged unusual use of a backend API key that had been leaked in a third party repository.

10. Monitor & Log API Activity Continuously

Log authentication events, authorization failures, input validation errors, and unusual spikes in usage. Centralize logs in SIEM systems for correlation and alerting.

Use anomaly detection to catch low and slow attacks that do not match known signatures.

Example: A global enterprise detected a cross tenant enumeration attempt because its SIEM alerted on a sudden spike in 403 responses from a single token.

11. Use an API Gateway or WAAP Layer

Place a gateway or WAAP in front of your services. Enforce authentication, schema validation, rate limiting, CORS, and threat detection before traffic reaches the backend.

A gateway provides uniform controls and prevents insecure microservices from being exposed directly to the internet.

Example: A misconfigured internal microservice never became a breach vector because the gateway blocked all unauthenticated access by default.

12. Maintain API Inventory & Documentation

Track all APIs, including internal microservices, partner APIs, beta versions, and deprecated endpoints. Shadow APIs and zombie APIs are the top contributors to enterprise breaches.

Use discovery tools that detect endpoints based on real traffic patterns.

Example: A telecom company identified 20 undocumented endpoints reachable from the public internet after discovery tools revealed traffic engineering teams did not know existed.

13. Test APIs Continuously

Run automated security scans in CI pipelines. Use fuzzing, schema testing, and negative tests to find issues early. Perform annual penetration tests on high risk APIs.

Treat every security finding like a failed functional test. Patch and retest immediately.

Example: A media platform caught a BOLA vulnerability during automated regression tests because the test suite included checks for cross user access after every release.

14. Build Security into the SDLC for APIs

Make API security part of how you design and ship software, not a final checklist. During design, run lightweight threat modeling for each new or changed API. Ask simple questions such as: what can go wrong if this endpoint is abused, which objects can be enumerated, and what happens if an attacker controls this field.

Embed security checks into code review. Require reviewers to confirm that authentication, authorization, input validation, and rate limiting are present on new endpoints. Add automated checks in CI for common issues such as missing auth, open HTTP listeners, or unsafe headers.

Example: A fintech team added a security review step for any endpoint touching payment flows. That single control caught a new refund API that initially lacked tenant checks, preventing a cross account refund abuse before it ever reached production.

15. Keep API Dependencies and Configurations Hardened

REST APIs depend on frameworks, libraries, API gateways, and cloud services. Vulnerabilities often appear in these supporting components rather than your own business logic. Maintain an accurate software bill of materials for each API service and continuously scan dependencies for known CVEs. Patch high risk libraries on a defined timeline and avoid running unsupported versions of frameworks or runtimes.

‍Example: A digital services team avoided a public exploit of a critical framework flaw because their dependency scanning flagged the vulnerable version during a routine build, and the release pipeline blocked deployment until the library was upgraded.

REST API Security Checklist: Identity, Input Safety, Transport Security & Hardening

This checklist provides a practical reference for reviewing REST API security controls and ensuring they meet modern enterprise standards. For clarity and ease of use, the checklist is divided into focused categories aligned to core security functions.

Identity, Access and Authorization

• Authenticate every request. Require valid API keys or tokens for all endpoints except those intentionally public. Validate tokens server side on every call.
• Enforce fine grained authorization. Apply object level access checks on every resource. Users or clients must only access their own data. Use roles and scopes and return 403 when access is not permitted.
• Adopt least privilege everywhere. Limit actions per client, per role and per service. Separate admin operations from user operations and protect them with stronger controls.
• Use Zero Trust for internal calls. Apply the same authentication and authorization policies to service to service traffic. Require mTLS or signed tokens internally.

Input, Output and Payload Safety

• Validate all inputs. Enforce strict schemas for every parameter and payload. Reject anything outside expected types, ranges or patterns.
• Escape and sanitize all outputs. Remove sensitive fields before sending responses. Encode any data that client applications may render.
• Protect against injection. Use parameterized queries exclusively. Never concatenate input into SQL, NoSQL, shell, or file system operations.
• Harden file and data handling. Restrict file types, scan uploads and disable unsafe XML features such as external entities.

Transport and Data Protection

• Use HTTPS everywhere. Enforce TLS 1.2 or higher. Block plaintext HTTP. Prefer TLS 1.3 for improved security and performance.
• Encrypt sensitive data at rest. Use AES 256 or equivalent, backed by proper key management. Hash passwords using adaptive algorithms such as bcrypt.

Secrets and Key Management

• Secure all secrets. Store keys and credentials in a vault or managed secrets service. Never embed secrets in code, mobile apps or config files.
• Rotate keys regularly. Replace keys and tokens on a defined cadence and immediately upon suspected compromise.
• Do not log or expose secrets. Never place credentials in URLs. Mask tokens in logs.

Abuse, Bots and Availability Controls

• Enforce rate limits and quotas. Apply per user, per IP and per key limits. Use 429 responses when thresholds are exceeded.
• Throttle brute force attempts. Apply strict velocity limits on login and token endpoints. Use lockouts or exponential backoff.
• Detect and block automated abuse. Use IP reputation, behavioural analysis and bot mitigation to stop scraping, credential stuffing and scripted attacks.

Monitoring, Logging and Visibility

• Log all critical activity. Capture authentication events, access attempts, failures and sensitive operations, with timestamps and source details.
• Centralize and monitor logs. Use a SIEM for correlation, anomaly detection and alerting on suspicious behaviour.
• Protect log integrity. Send logs off box in real time and ensure retention policies align with forensic and regulatory needs.
• Maintain an API inventory. Track every API (internal and external), its owner, data classification and exposure level. Identify shadow and deprecated APIs.
• Remove unused or legacy endpoints. Retire old API versions quickly. Zombie APIs are high risk attack surfaces.

Architecture and Perimeter Controls

• Use an API gateway or WAAP. Enforce centralized authentication, schema validation, rate limits, threat detection and global policies at the edge.
• Configure CORS safely. Only allow approved origins. Do not use wildcard settings unless the API is genuinely public.

Testing, Assurance and Response

• Test security continuously. Integrate SAST, DAST, API fuzzing and schema validation into CI/CD.
• Pen test regularly. Include business logic and BOLA testing, not just basic signature testing.
• Verify fixes with regression tests. Ensure previous vulnerabilities cannot reappear in future releases.
• Prepare an incident response plan. Know how to revoke tokens, rotate keys, isolate components and communicate with partners when an API incident occurs.

Future Trends in REST API Security (2026 and beyond): AI, Zero Trust, GraphQL, gRPC & More

REST API security is evolving quickly. Attackers are moving faster, automation is rising, and API footprints are expanding across cloud, mobile, and distributed architectures. 

The following trends represent where API security is headed next, and where enterprise leaders should focus to stay ahead.

1. Zero Trust Applied to Every API Call : Zero Trust principles are now extending fully into API ecosystems. Even internal API traffic is treated as untrusted. Expect widespread adoption of mutual TLS, short lived signed tokens, continuous authorization checks, and the removal of all “trusted network” shortcuts. With APIs remaining the top application attack vector in recent industry studies, Zero Trust enforcement at the API layer is becoming unavoidable.

2. AI Driven Detection for API Abuse and Anomalies: Machine learning systems are increasingly used to baseline normal API behavior and flag deviations such as subtle data exfiltration, credential stuffing patterns, or business logic misuse. AI is critical because automated threats now account for a significant portion of API attacks; around 30% of malicious API traffic involves bots, and ~17% targets business logic weaknesses. Future platforms will use AI not only for detection but also for automated containment (for example, isolating suspicious tokens or dynamically challenging risky clients).

3. Expanding Security Patterns Beyond REST: Organizations are adopting GraphQL, gRPC, event driven APIs, and mixed architectures. GraphQL introduces risks like excessive complexity queries, schema introspection leakage, and field level access issues. Expect new standards and security tooling to address this, including query depth limiting, field level authorization, and stronger schema governance. OWASP and major vendors are already publishing new guidance for securing emerging API types.

4. Regulatory Pressure and Formal API Requirements: As APIs become the primary access point for personal and financial data, regulators are taking direct interest. Expect tighter audit expectations around API logging, encryption, consent enforcement, and Zero Trust aligned access control. Research tying 11.8% of global cyber losses to API and bot attacks is accelerating this shift. Open Banking, healthcare APIs, and data protection frameworks are likely to define explicit API security baselines.

5. Automated API Security Testing and Continuous Validation: API security testing is shifting left. New tools continuously fuzz APIs, validate authentication flows, and probe BOLA and mass assignment scenarios. These capabilities are increasingly integrated into CI/CD so every release is automatically tested. Enterprises are adopting this because API changes occur far more frequently than traditional pen testing cycles, creating exposure gaps that automation can close.

6. Unified API Security Platforms: Instead of separate tools for discovery, gateway enforcement, WAF, scanning, and anomaly detection, enterprises are consolidating toward integrated API security platforms. 

These provide:

• continuous discovery of shadow/zombie APIs,
• inline protection (WAAP),
• active testing and fuzzing,
• and unified analytics.

This consolidation reflects a need for complete coverage, given the average enterprise now has 30–40% of APIs untracked or undocumented.

7. Security Embedded Into Frameworks and Tooling: Languages, frameworks, and cloud middleware are beginning to bake in secure defaults; such as auto applied object level authorization filters, automatic JSON schema validation, or enforced secure headers. This shift aims to reduce developer error, which remains the root cause of many API breaches (hardcoded secrets, missing auth, excessive exposure, etc.).

8. Third Party and Supply Chain API Risk: Enterprises increasingly depend on third party APIs. That creates supply chain risk: if a partner’s API is compromised, the breach can cascade. Expect more rigorous onboarding assessments, contractual security requirements, and automated monitoring of external API behavior. The rise of SBOM and API inventories will extend into this domain.

9. Deception and Early Warning Techniques: Advanced defenders are starting to deploy honey APIs, fake endpoints, and honeytokens embedded in API responses. These give immediate alerts when an attacker begins probing or enumerating. While not yet mainstream, this approach is growing as organizations seek earlier signals of API reconnaissance.

10. IoT and Edge API Security Becomes Critical: IoT, vehicle systems, industrial devices, and edge platforms rely heavily on lightweight APIs. These often lack robust authentication, and many operate outside traditional firewalls. Expect secure device identity, end to end encryption, and cloud validated authorization models to become mandatory as attacks shift toward distributed edge environments.

Strengthen REST API Security with Levo.ai: Continuous Testing & Runtime Protection

The security landscape for APIs continues to expand. More endpoints. More machine to machine traffic. More automation from both defenders and attackers. 

As this guide outlines, building secure APIs requires consistent authentication, airtight authorization, rigorous input validation, continuous monitoring, rate limiting, and continuous security-testing. 

The challenge for large enterprises is implementing and automating these practices at scale, not a lack of awareness around which practices need implementation.

This is where Levo.ai provides meaningful leverage.

Modern REST API security requires continuous protection; not just in production, and not just during development. Levo secures APIs holistically across the entire lifecycle, from design and build time to deployment and runtime operations. By combining Shift Left testing, Shift Right protection, and continuous visibility, Levo ensures that API risks are identified early, validated often, and mitigated instantly in production.

1. During Development & the SDLC: Shift-Left API Testing and Governance

• Levo’s API Discovery, API Documentation, and API Security Testing modules integrate early in the software delivery lifecycle to eliminate vulnerabilities before they reach production.
• Automatic API Discovery & Inventory: Levo continuously identifies every API, documented or not, and maps endpoints, methods, parameters, authentication rules, and data flows. This forms the foundation for governance and secure-by-design development.
• Accurate, Always Current API Documentation: By generating and maintaining OpenAPI specifications directly from observed behavior, Levo removes drift between code, docs, and deployed services, preventing outages, mismatches, and integration failures.
• Continuous API Security Testing: During build, integration, and QA stages, Levo stresses APIs with real attack patterns, validates authentication and authorization logic, uncovers business logic flaws, and flags schema drift before it becomes a vulnerability.
• These shift-left modules ensure developers catch issues when remediation is fastest and cheapest.

2. In Production: Runtime API Threat Detection & Protection

Once APIs are live, Levo’s Runtime API Protection and Threat Detection modules provide real-time defense without the brittleness of traditional WAFs.

• Behavior based threat Detection: Levo monitors live traffic to detect anomalous activity, unusual authentication behavior, sensitive data exposure, API abuse patterns, and OWASP API Top 10 risks.
• High-Precision Blocking & Adaptive Enforcement: Instead of relying on static signatures, Levo uses real behavioral patterns and context to block attacks with high accuracy—reducing false positives and eliminating operational friction.
• Sidecar and eBPF Level Context: Lightweight sensors inside your environment observe traffic without adding latency, preserving privacy, and avoiding the maintenance burden of legacy WAF architectures.

3. Continuous Posture Management Across Both Domains

Levo unifies dev-time testing and runtime defense into a single posture view:

• Track improvement and risk reduction over time
• Identify vulnerabilities introduced during development.
• Highlight threats observed in production.
• Prioritize fixes with guided remediation workflows.

This lifecycle approach ensures that REST APIs are discovered, documented, tested, monitored, and protected—continuously and automatically.

If you want to see Levo’s Runtime API Security Platform in action, the Levo team can walk you through it live.