An insufficiently secured API is an open door to customer data, payment information, or internal systems. Good API security relies on a combination of strong authentication, encryption, access management, and continuous monitoring. In this article, you’ll find concrete best practices you can apply right away, whether you’re building your own application or managing integrations between existing systems.
Authentication and authorization
It starts with the question: who is allowed to call this API, and what are they allowed to do with it? Always use a standardized method such as API keys, OAuth 2.0, or JWT tokens instead of custom-built logic. Important principles:
- Give each user or application its own key or token, so you can revoke access per account.
- Separate authentication (who you are) from authorization (what you’re allowed to do) and verify permissions again with every call.
- Use the principle of least privilege: only grant access to the endpoints and data that are truly necessary.
- Let tokens expire after a period of time and provide a way to refresh them.
Encryption and secure connections
All traffic to and from an API should go over HTTPS, never unencrypted HTTP. A valid SSL certificate is the foundation for this. Many hosting providers, including Tandata, offer free SSL certificates that are automatically installed and renewed via web hosting with Plesk, so you don’t have to manage this manually.
In addition, encrypt sensitive data at rest, for example in the database, and avoid sending passwords or full credit card details in API responses. Only send the fields the calling party actually needs.
Rate limiting and abuse prevention
Without limits, an API can easily be flooded with requests, whether intentional or not. Rate limiting restricts the number of calls per user or IP address within a certain period, preventing overload and brute-force attacks on login endpoints.
Also always validate input server-side, even if the client already performs checks. Only accept expected data types and lengths, and reject unknown fields instead of silently ignoring them.
Logging, monitoring, and server settings
Good logging makes it possible to quickly detect abuse and analyze it afterward. At a minimum, log: who made a call, when, from which IP, and whether the call was successful. Avoid logging passwords or full tokens.
Also make sure the underlying server and software stay up to date. If you manage your own environment via Plesk, you’ll find the settings for SSL, firewall rules, and PHP versions all in one place. A stable environment with NVMe storage and daily backups also helps: if an attack does cause damage, restoring to an earlier version is quick and easy.
Choose an authentication method
Implement tokens or API keys per user, with limited validity.
Enforce HTTPS
Put all endpoints behind a valid SSL certificate and reject unencrypted requests.
Set rate limits
Limit the number of calls per user and monitor peak loads.
Validate and log
Check input server-side and record relevant call data for analysis.
Keep systems updated
Regularly update software and dependencies and check backups.
Does your API also use email notifications, for example for verification links or alerts? Then make sure the underlying business email is properly configured with SPF, DKIM, and DMARC, so messages aren’t marked as spam or misused for spoofing.
Frequently Asked Questions
Is an API key enough for security?
An API key alone is a basic form of identification, but it doesn’t provide complete security. Always combine it with HTTPS, permission checks, and rate limiting.
Should I secure internal APIs too?
Yes. Internal connections between systems should also be authenticated and encrypted, because otherwise a compromised component immediately grants access to other systems.
How often should I expire tokens?
This depends on the sensitivity of the data, but shorter validity periods with a refresh mechanism are safer than long-lived tokens.
What is the difference between authentication and authorization?
Authentication confirms who the caller is, authorization determines which actions and data this caller is allowed to use.
Conclusion
API security is not a one-time setting but an ongoing process of strong authentication, encrypted connections, rate limiting, and active monitoring. By combining these layers, you significantly reduce the attack surface and limit the damage if something does go wrong.