API Security Best Practices: 7 Proven Ways to Stop Hacks

To apply API security best practices , you first need to understand who might attack your system and how they think. The OWASP Top 10 for API Security is a great starting point, as it explains the most common weaknesses that hackers exploit. For example, one of these issues is called Broken Object Level Authorization (BOLA), which happens when an API accidentally gives users access to data that isn’t theirs.

Many of the vulnerabilities that would be used to commit an API attack can be linked back to “shadow APIs,” which are either endpoints that were never fully developed or documented, or old endpoints that continue to exist due to lack of timely updates or security patches. Attackers will typically look for and target these older versions to use them to bypass the more advanced security protections on your new version (i.e., using an older version like /v1/ as opposed to /v2/) to obtain sensitive user information.

Excessive Data Exposure is another significant threat to your API. As an example, many APIs will send back a full JSON object to the frontend, and many require the UI to filter out the excess data. An attacker can simply capture the raw response to obtain access to all data, including hidden fields containing, for instance, administrative status and private email addresses.

Authentication tells us who a person is, but Authorization tells us what a person can do. In order to have the best possible security practices with APIs, you should take advantage of current methods of securing identity through OAuth2 and OpenID Connect, which are much more secure than using simple API keys.

You should implement access using the concept of ‘Least Privilege’ by implementing Scopes. Instead of giving a third-party application complete access to a user’s account, give them a token that is ‘scoped’ to allow only access to non-sensitive resources that are ‘read-only’ in nature and are necessary to complete the task you asked of them.

Finally, when using JSON Web Tokens, an application must proceed with caution. Your backend should validate every token’s signature and expiration. Sensitive information should never be stored in a JWT payload because it is so easy to decode a JWT payload by anyone who has intercepted it.

To properly secure your API, you must encrypt your information. This includes using Transport Layer Security (TLS) 1.2 or 1.3 for all data in transit, protecting against Man-in-the-Middle (MITM) attacks when hackers are trying to steal login credentials and session tokens by “sniffing” traffic.

The data at rest can also be vulnerable. It is important to encrypt sensitive fields in your database. For example, by encrypting personally identifiable information (PII) and API secrets. Adding a Hardware Security Module (HSM) and/or using a cloud-based Key Management Service (KMS) will provide an additional layer of protection.

Mobile applications should implement Certificate Pinning to only allow the application to talk to a server with a specific, pre-defined certificate so that attackers cannot use a fraudulent certificate to intercept your API calls.

It is essential that you do not rely solely on the information supplied by Clients when implementing security measures for APIs. Verifying all incoming data from clients is the foundation for proper API protection. Attackers will send in corrupt or malformed data to create SQL Injection attacks or Cross-Site Scripting (XSS) attacks that can completely compromise your server infrastructure.

Take a Deny by Default stance for your API. Every parameter sent to your API should always be validated against a known good format for its type and should match the specifications set forth by you. For example, if an API requires an ID that is numeric, any request sent with strings or special characters should automatically be rejected.

When sending data back to users, validate the data before sending it back. For example, when sending data that has been captured from user input and reflecting that data in a response to a user via a web browser, encode the data before sending it back so that it is not executed. This ensures that many common forms of injection, such as SQL Injection and Cross-Site Scripting (XSS), do not exist.

Brute force and denial-of-service (DoS) attacks are common forms of malicious activity targeting APIs. Therefore, it is important to implement rate limiting as a best practice within the context of API security; it is one way to throttle the maximum number of requests a user may make at any one time during a given period of time.

Throttling services can also help slow down request processing for those who are approaching their limit, which allows you to conserve resources and ensure that no single ill-intentioned or poorly designed client can take down your service, thereby maintaining access to the services for other legitimate users.

The API gateway serves as an additional layer of protection by controlling all API traffic prior to it reaching your microservices. This allows your application to reduce its attack surface area.

Real-Time Logging and Auditing for API Security Best Practices

To defend against an attack, you must first know about it. High-level API Security Best Practices include Real-Time Logging for All API Activity. This means logging not only successful Authentication attempts but also Failed Authentication attempts and access to sensitive resources (i.e.: /admin; /payments).

Auditing will prove to be important in the post-incident analysis phase of an incident. The logs should contain the Request Timestamp, Caller’s IP Address, Requested Resource, and the Response Code to be useful to you in conducting the analysis of the incident; however, you should not ever log sensitive information such as Passwords, Private Keys, or Complete JWT tokens.

You’ll want to integrate your logs with a Security Information and Event Management (SIEM) Tool, Set-Up Automated Alerts for any “Spikes” In Anomaly (for example, if you see a sudden increase of 500% in the number of 401 Unauthorized Errors this is most likely an indication that a Credential-Stuffing Attack is currently In Progress).

You should incorporate Security as part of your Development Life Cycle rather than trying to add it once the application is completed. Activity such as source code analysis should be conducted when you are committing code and include scanning for hard-coded API Keys and other insecure libraries using Static Application Security Testing (SAST) Tools.

A best practice for API Security in DevOps is Secret Management. By using Secret Management tools like HashiCorp Vault or AWS Secrets Manager, you can replace plain-text configuration files with run-time injected credentials.

The automated scanning of dependencies is also critical. Most API breaches are caused by a vulnerability in an open-source package that was included in the development. Snyk or GitHub Advanced Security are examples of tools that provide you with notifications when a library used in your application has a known security vulnerability that needs to be patched.

Testing and Assessing API Security

The only way to check or confirm how strong or resilient your defenses are, is to conduct regular tests. Dynamic Application Security Testing (DAST) tools perform a complete scan of your “live” API in order to identify vulnerabilities, such as a lack of encryption on endpoint data and a missing HTTP Security headers, which may have been missed by your code-scanning utilities.

AT LEAST once a year, conduct a Manual Penetration Test. Automated testing tools can be very effective, but only an experienced human Ethical Hacker will be able to find more complicated or complex security vulnerabilities, such as business logic manipulation (altering a business process so that you can obtain a discount) or evading a paywall.

Fuzz Testing is another key technique to find hidden vulnerabilities. By sending large amounts of random and unexpected data to your API Endpoint, you can discover unexpected situations (or “Edge Cases”) that may result in a crash or memory leak, thus highlighting potential stability and Security issues.

API Security Best Practices – 20-Point Checklist

1. 1. Use HTTPS Everywhere
   Always secure your API traffic using TLS 1.2 or higher to prevent data interception during transmission.
2. 2. Enforce Strong Authentication
   Implement OAuth 2.0 or OpenID Connect to ensure only verified users and systems access your API endpoints.
3. 3. Apply Role-Based Authorization
   Limit data access to user roles to prevent unauthorized actions and maintain principle of least privilege.
4. 4. Validate All Inputs
   Check every parameter against expected formats to block injections, malformed data, and malicious payloads.
5. 5. Rate Limiting and Throttling
   Protect your API from brute force and DoS attacks by restricting request volume per user or IP.
6. 6. Protect Against Data Exposure
   Filter sensitive fields in responses, returning only what the client truly needs to function.
7. 7. Monitor with Logging Systems
   Track every API request, especially failed logins or admin endpoint access, for real-time threat visibility.
8. 8. Use a Secure API Gateway
   Centralize traffic management and enforce policies to reduce your application’s attack surface area.
9. 9. Encrypt Sensitive Data at Rest
   Secure PII and tokens using database encryption and key management solutions like AWS KMS or Vault.
10. 10. Implement Secret Management
    Never hard-code credentials; inject them securely at runtime using secret management tools.
11. 11. Keep Dependencies Updated
    Regularly scan and patch vulnerable open-source libraries used within your application stack.
12. 12. Perform Static Code Analysis
    Use SAST tools to detect insecure coding patterns and embedded secrets during development.
13. 13. Conduct Dynamic Security Testing
    DAST tools help uncover live environment issues like missing headers or misconfigured endpoints.
14. 14. Schedule Manual Penetration Testing
    Human ethical hackers can identify business logic flaws automated tools might overlook.
15. 15. Implement Fuzz Testing
    Send random, unexpected data to your API to expose edge cases that could cause crashes or leaks.
16. 16. Adopt a Zero-Trust Approach
    Never assume any client or internal service is trustworthy; always verify identities and requests.
17. 17. Secure CORS Configurations
    Restrict allowed domains and HTTP methods to prevent unauthorized browser-based access.
18. 18. Disable Unused Endpoints
    Remove legacy or testing APIs that attackers could exploit to bypass updated security layers.
19. 19. Integrate with a SIEM Tool
    Automate log analysis and anomaly detection for faster identification of live attacks or irregularities.
20. 20. Build Security into CI/CD Pipelines
    Automate code scans, dependency checks, and policy enforcement before each deployment to maintain continuous protection.