When configured correctly, Application Programming Interfaces (APIs) enable seamless data exchanges across platforms, assisting with cross-app integrations and making microservices possible.

As APIs have become integral in modern applications, we as developers must learn how to protect them against impending threats. The State of API Security report found that 74% of respondents have experienced at least three API-related breaches since 2021, so the threat here is very real.

In this article, you’ll learn about six important ways to protect APIs against common vulnerabilities. Let’s get started.

1. Strong Authentication and Authorization

Authentication is the first line of defense, as it ensures that only legitimate users can interact with the API.

There are several mechanisms to achieve strong authentication:

• OAuth. The most popular open-standard protocol, which enables users to grant access to resources without exposing credentials. It’s ideal for situations where third-party services need to access an API on a user’s behalf.
• API keys. A simple way to authenticate API requests by assigning a unique key to each client that attempts to access the API.
• JSON Web Tokens (JWT). Signed tokens used to securely transmit information between parties. JWTs are often used for stateless authentication, meaning that the server doesn't need to store any session data.

But authentication is just one piece of the puzzle. You also need authorization mechanisms based on user roles or permissions to prevent unnecessary exposure. Another thing to remember is to avoid hardcoding credentials in your codebase. Instead, use environment variables or secure vaults to store sensitive information.

2. Secure API Endpoints

Attackers can easily scan for public-facing API endpoints, and then look for vulnerabilities to exploit. The first step is to limit the number of exposed endpoints in the first place, ensuring that only essential endpoints are accessible.

One way to accomplish this is by using an API security solution with endpoint discovery capabilities, which will help you identify and map all exposed API endpoints. From there, you can monitor and assess their status and take action to address vulnerabilities or remove unnecessary endpoints.

For example, if there are any older “legacy APIs” that are unmaintained, you should remove them immediately, as they are often the ones that attackers exploit due to lack of updates.

3. Validate and Sanitize Data Input

One of the most basic ways an attacker can abuse APIs is through injection attacks. Injections are relatively simple, but many applications and APIs remain vulnerable due to inadequate input validation and data sanitization practices.

Make sure that all incoming data in input fields is validated for expected formats, character types, and length. For example, you might specify that no special characters be allowed in usernames.

It’s also a good idea to use parameterized queries to separate queries from the relevant data inputs. This will treat all user-supplied data as a value rather than executable code, preventing attackers from injecting harmful SQL commands. It’s important to take these steps both at the client and server sides, to ensure all inputs are thoroughly vetted before interacting with the application logic.

4. Rate Limiting and Throttling

Apart from injection, APIs can also be targets of Denial of Service (DoS) attacks, which overwhelm the server with an excessive number of requests, causing it to slow down or crash. To mitigate this, implement rate limiting to control the number of requests a single user or IP address can make within a specified time frame, protecting against DoS and brute-force attacks.

Essential API calls, like those involving critical business functions, should be given more bandwidth and higher rate limits so that non-essential functions don’t disrupt their availability.

Depending on the type of application you’re running, you could also introduce flexible rate limits to allow users with special permissions or subscriptions to make more requests without experiencing disruptions.

5. Encrypt Data At-Rest and In-Transit

Encrypting sensitive data, especially Personally Identifiable Information (PII), ensures that even if a breach occurs, the data is unreadable and unusable for unauthorized users. It’s important to encrypt data both on your servers (at rest) and while being transmitted between servers or clients (in transit).

The go-to encryption protocol for data at rest is AES-256, while data in transit should use TLS (Transport Layer Security). But remember that hackers are sneaky, so simply implementing encryption is only the first step. Encryption keys can easily be compromised, which is why you need additional measures.

One that immediately comes to mind is key rotation, whereby encryption keys are regularly updated and replaced, limiting the time a single key can be used to gain access. Another measure is to store encryption keys securely, using a dedicated key management system (KMS). You should never hardcode keys into the application code itself.

6. Use API Gateways and Web Application Firewalls (WAFs)

It’s highly recommended for developers to use an API gateway, especially on large-scale applications, as it provides a central location for managing security functions like authentication and authorization, policies, and traffic.

For managing traffic, a web application firewall (WAF) can also be very beneficial. The WAF can filter and monitor incoming API requests, blocking known malicious patterns.

If all of the other security measures fail, the WAF will likely stop any common attacks, including DDoS and injection attacks.

Conclusion

APIs have become essential for the smooth integration of applications and services. But with their rise comes increased security risks, as hackers continuously look for vulnerabilities to exploit.

Implementing the security measures outlined in this article, and being proactive about securing your APIs from newer techniques that attackers may use is crucial to ensure the integrity and long-term security of your systems.