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API Security
Best Practices:
The Ultimate Guide

Nicole Jones

Nicole Jones|January 2, 2024

Master API security essentials with our comprehensive guide. Dive into the importance of safeguarding APIs, from REST to GraphQL, and learn the latest best practices to protect against cyber threats. Explore robust authentication, encryption, and secure infrastructure strategies with real-world tips for implementation. Perfect for developers and IT professionals, this guide ensures the integrity and confidentiality of your digital interactions remain secure. Enhance your API security with actionable insights and advanced protective measures. Protect your applications today and fortify your defenses with our expert advice on API security.

Application Programming Interfaces (APIs) have become a staple in almost every application and software we develop. They make up the fabric of how we, as developers, communicate and exchange data between applications. From the bustling data exchanges of global financial systems to the subtle, everyday interactions within a smartphone app, APIs are core to functionality that users expect. However, the critical role of APIs extends beyond just the functionality they provide; they are also vital to safeguarding sensitive data and systems against cyber threats. As APIs continue to boom in both usage and complexity, the imperative need to secure them has never been more critical.

This guide will explore many facets of API security to give you the knowledge to fortify your APIs against many potential security threats. This guide delves into the nuanced layers of API security, from the fundamentals to advanced protective strategies, ensuring that the integrity and confidentiality of your users' digital interactions remain secure and uncompromised. Whether securing a RESTful service or navigating the new world of GraphQL, this guide covers the complete landscape of API security to bring you the most effective and current best practices for keeping your APIs safe. Let’s start by looking at the most fundamental of all questions: what is API security?

What is API security?

API security is the protective shield between your APIs and the multifaceted threat landscape that is the byproduct of the interconnected nature of today’s digital ecosystem. API security itself is composed of many different aspects, spanning different protocols, systems, and tools. Each of these facets is designed to prevent malicious attacks on or through APIs, helping to protect the building blocks of modern software communication. 

API security ensures that only authorized users can perform authorized actions at their most basic level. This is generally achieved through implementing robust authentication and authorization processes. These processes help to confirm user identities and grant permissions appropriately. Encryption also plays a critical role here, serving as a vital tool to protect data as it moves between servers and clients. But API security doesn't stop at access control; it also involves monitoring and logging API activity to detect and stop potential threats, implementing rate limiting to prevent abuse, and managing the API lifecycle to mitigate vulnerabilities that attackers could exploit.

Unlike other processes within the software development lifecycle, API security is not a one-time setup but a continual process. API security must evolve with the changing threat landscape and adapt to new types of APIs, such as what we saw with the advent of GraphQL, and the latest integration patterns. The goal is to create a secure environment for data exchange that upholds data integrity, availability, and confidentiality while minimizing the attack surface that attackers could exploit.

Why is API Security important?

With the pivotal role that APIs play in modern software and applications comes a significant risk; by their nature, APIs are exposed to the open internet, making them a prime target for cyberattacks. The importance of API security stems from the need to protect sensitive data transferred between services, safeguard user privacy, and ensure malicious actors do not disrupt critical business operations through an attack.

As we have seen within the last few years, the stakes of API security breaches are high. Such incidents can lead to data theft, service outages, and significant financial losses. For instance, an unprotected API could allow an attacker to siphon off sensitive customer data, resulting in identity theft and fraud. Often, we think about databases being compromised, leading to data breaches; however, this same data can also be leaked via API. Due to these breaches, businesses may face regulatory penalties for failing to protect user data, with many standards and penalties being outlined in protection laws like GDPR and HIPAA that govern many industries.

API security, whether users fully understand it or not, is a big part of the trust users place in digital services. A single breach can severely impact a company's reputation, causing a loss of customer trust and loyalty. Even more important is that one vulnerable API can have many ripple effects due to the interconnected fabric of different services. An example would be if a compromised API is associated with other services and partners, amplifying the impact of a breach.

Therefore, API security is not just a technical necessity but a business imperative. A solid approach and framework to API security are essential to ensuring that your organization offers a secure service for your users.

How do you secure a REST API?

Securing REST APIs starts from the ground up, preferably from the outset of building said APIs. Making sure that a REST API is secure has to be approached from many different angles. REST, or Representational State Transfer, is a type of API that uses standard HTTP methods and is highly popular for its simplicity and statelessness. However, the same features that have led to the popularity of REST can be exploited if not properly secured. Let’s look at some basic security features and patterns to implement to secure a RESTful API.

Firstly, you’ll want to implement Transport Layer Security (TLS) to ensure that all data transmitted between the client and server is encrypted. One of the easiest ways to do this is to use an API gateway that allows you to use TLS, preferably mutual TLS (mTLS), if available. Utilizing TLS functionality in your REST API mitigates the risk of data interception and unauthorized access during transmission. It’s a fundamental step that forms the baseline of REST API security.

Secondly, authentication mechanisms are critical and should be implemented as well. Again, any API gateway or API proxy can be used to add this functionality easily. You often use an already established identity provider (IdP) such as Okta or Auth0 to generate tokens and manage identity. API keys or, more commonly, auth tokens, such as JSON Web Tokens (JWT), are a common method for securing REST APIs. Tokens can help to ensure that only authenticated users can access certain endpoints. These tokens can also contain scopes and permissions that can be used for authorization, ensuring that users can only perform the authorized functions. Tokens and API keys are preferred over basic authentication because they do not require transmitting usernames and passwords with each request, a practice that also comes with risks.

Lastly, input validation is another essential practice that should be implemented. The basic principle applied here is that REST APIs should never trust the data they receive. Many API frameworks have various mechanisms to help with this, one of the most crucial being using the correct mechanisms for any database query. Rigorous validation of all incoming data helps to prevent common vulnerabilities like SQL injection and cross-site scripting (XSS). This involves validating the types of data and sanitizing it to ensure that malicious input is neutralized before it has the chance to do any damage. For those using an Open API Specification (OAS), formerly known as a Swagger specification, you can also use this document to verify that incoming data matches the data type expected for each field and some other attributes. However, this should only be used as a preliminary check as a supplement to good input validation built into your code.

These foundational security measures are “must-implement” pieces for anyone creating REST APIs. Of course, many other advanced security features should be added for further protection that will be outlined in the best practices section later in the guide.

Learn more about securing REST APIs here.

How do you secure a GraphQL API?

Next, we will look at securing one of the most recent API technologies, GraphQL. As the adoption of GraphQL grows, GraphQL APIs present a unique set of security challenges. Due to GraphQL’s query language and other features that make it more flexible than traditional API technologies, a new approach must be taken to secure the data within them. Unlike REST, which uses defined endpoints with defined requests and responses, GraphQL allows clients to query for exactly what they need, no more and no less. The dynamic nature of a GraphQL query or mutation can lead to some distinct security considerations.

First, much like what we discussed regarding securing REST API endpoints, ensuring that Authorization and Authentication are in place is crucial to safeguarding resources. Unlike REST, this becomes relatively complex with GraphQL. Ensuring the user is authenticated to use the GraphQL API can follow a similar pattern to REST, using many of the same mechanisms and technologies. The complexity comes with the authorization piece, where you may need the ability to control read and write access to certain fields within the GraphQL API. Some API gateway can help with this, as well as the GraphQL framework or platform you use to build the APIs.

Secondly, like REST, securing a GraphQL API requires developers to validate and sanitize all input to prevent malicious activity, such as injection attacks. With GraphQL, this is once again slightly more complex than other API technologies since queries and mutations can be complex and require validation and sanitization to be done at a granular and modular level.

Another important aspect of securing a  GraphQL API is managing query complexity to prevent resource exhaustion, resulting in a denial of service attack. For instance, a common way that GraphQL resources can be exploited is through batching attacks or deeply nested queries. You can mitigate such risks by putting a mechanism in place to limit the depth and breadth of queries, possibly through depth limiting or pagination. As of late, some API gateways that support GraphQL can add these checks and enforce them at a policy level.

One last consideration that is unique to GraphQL is to consider the implications of introspection. As users of GraphQL know, introspection is a feature in GraphQL that allows the querying of the schema through an introspection endpoint. While this is useful for developers who want to use the service, in production, it might give attackers insights into your API that could be exploited. In the case where the introspection endpoint can’t be disabled, you should think about severely restricting the amount of data that is exposed through the introspection endpoint.

By putting the above security measures and considerations into practice with your GraphQL development, you’ll have the base of a secure GraphQL API. It’s important, though, to remember that these strategies are part of a larger security posture, which we will look at further in the API Security Best Practices section later in the guide.

How do you secure a gRPC endpoint?

The last type of API we will look at will be gRPC. gRPC, a high-performance RPC (remote procedure call) framework created by Google, relies on HTTP/2 for transport and Protocol Buffers as its interface description language. To secure gRPC APIs, you must address the protocol and the message formats.

Firstly, similar to what was mentioned with the other types of APIs we covered, gRPC services should employ TLS for transport security. Doing this helps to ensure that all data transmitted via gRPC is encrypted and secure from interception. For message-level security, you should utilize the built-in authentication mechanisms provided by gRPC, such as token-based authentication, which can integrate with identity providers such as Auth0 and Okta.

Additionally, you’ll also want to make sure always to validate and sanitize all incoming data to prevent injection attacks. With gRPC's strict schema definitions, you can enforce message validation based on the defined Protocol Buffers. This can help detect abnormal messages that could be part of a potential attack, allowing you to add a mechanism to stop such malicious activity from becoming catastrophic to the system or data within it.

Lastly, you’ll want to implement fine-grained access control for the service. This is particularly important with gRPC due to its ability to create complex service-to-service interaction patterns. If such interactions go unchecked, attacks may be able to penetrate deep into the systems that are exposed through the gRPC calls. By implementing a robust access control strategy, you can ensure that services only have the permissions necessary to perform their intended functions.

Securing gRPC APIs also involves monitoring and logging all operations to detect and respond to suspicious activities promptly. Robust monitoring and logging also create an audit log, which can be used to see the impact of attacks if they do make it through your defenses. The principles above tie into the more advanced security measures and best practices we will cover later in this guide.

What are the principles of API Security?

When it comes to best practices, they are usually driven by underlying principles that help to inform them. Like other best practices, API security is underpinned by principles that guide the development and implementation of secure APIs. Drawing from the OWASP Top 10 for API Security, these principles can be summarized into key areas of focus, many of which we already touched on above. Let’s briefly look at these key areas, listed below, before diving into the best practices section of the guide.

Authorization and Access Control

Effective access control is crucial for securing APIs. It’s not enough to authenticate users; systems must also check that each user has the right to access or modify their requested resources. This involves implementing checks at both the object level (ensuring users can access only the objects they are permitted to) and function level (actions they can perform). For instance, OWASP highlights broken object-level authorization as a common issue, where APIs expose endpoints handling object identifiers, creating a broad attack surface for unauthorized access.

Authentication Integrity

Authentication is the first line of defense regarding API security. A robust authentication process ensures that only legitimate users can access the API. OWASP notes that broken authentication is a common risk, where attackers compromise authentication tokens or exploit flaws to assume other users' identities. Solutions like multi-factor authentication, token blacklisting, and the use of short-lived access tokens can help to mitigate this risk significantly.

Data Exposure and Validation

With data being collected continuously, private and sensitive data is abundant within the API landscape. Excessive data exposure occurs when an API sends more data than necessary to the client. To combat this, data should be carefully validated on both input and input to protect the system from malicious data and to ensure sensitive information isn’t exposed to the client. OWASP combines this principle with mass assignment vulnerabilities, where attackers exploit overly wide permissions to modify data they shouldn’t have access to. A mechanism such as an allowlist for data processing and output can help prevent such exposures.

Resource Management

Slightly different than our other principles, this principle is more rooted at the infrastructure level. Here, we are focused on conserving and allocating server resources to prevent service outages or degraded performance. This could be due to a malicious attack or an unintentional issue with how the client uses the API. OWASP identifies unrestricted resource consumption as a potential risk, which can lead to denial of service or increased operational costs. By implementing rate limiting, quotas, and other controls, you can manage the load on the API and its underlying services to ensure that everything stays within the anticipated ranges.

Configuration Management

Another factor affecting infrastructure is proper configuration management. By following the proper protocols and best practices for configuration, you can ensure that security settings are defined, implemented, and maintained as intended. Misconfigurations can lead to security gaps and are often cited by OWASP as a prevalent risk within the API ecosystem. Regularly reviewing and updating configuration settings, automating configurations through Infrastructure as Code (IaC) practices, and employing configuration management tools can help maintain a strong security posture throughout all your environments and applications.

Secure Dependencies

Our last principle revolves around the code that our APIs and applications rely on. Dependencies, such as third-party libraries and APIs, can introduce vulnerabilities we may not be aware of. OWASP cautions against the unsafe consumption of APIs and dependencies, where developers may inadvertently trust these third-party resources without proper security consideration. Conducting regular security reviews of third-party services, using Software Composition Analysis (SCA) tools to detect vulnerable components, and applying security patches promptly are key strategies for securely using dependencies.

The principles above form the bedrock of secure API design and operation. By adhering to these principles, organizations can create secure APIs that meet functional requirements. Successful organizations must resist the advanced threats that target today's digital infrastructure, especially when it comes to their APIs.

API Security Best Practices

Now that we have covered all of the basics, it’s time to put these concepts into practice by looking at API security best practices. In this list, we will comprehensively go over different tools and strategies you can use to make sure your APIs are as secure as possible. Let’s dive into the API security best practices you should be applying to your APIs.

Conduct Regular Security Audits and Penetration Testing

First, security audits and penetration testing are needed to test your API’s security protocols. These testing methods are designed to uncover and address vulnerabilities early in development. Regular security audits involve comprehensively examining your API's infrastructure, policies, and codebase to ensure compliance with security standards. Penetration testing, on the other hand, involves simulating cyberattacks to test the resilience of your API against real-world threats.

To implement this, you should schedule regular audits within your development cycle and after any major changes to your API. By using a tool like StackHawk, you can automate vulnerability testing, while hiring external penetration testing teams can provide an outsider's perspective on your API's security. Regular testing helps identify authentication, authorization, and processing logic weaknesses that attackers could exploit.

Implement Strong Authentication and Authorization Checks

Next in importance is authentication and authorization. These mechanisms form the gateway through which access to your API is regulated. As we covered earlier, authentication verifies the identity of users, while authorization determines what they should have access to. A weakness in these areas can lead to unauthorized access and potentially full system compromise.

To implement authentication and authorization, adopt protocols like OAuth 2.0 and OpenID Connect to manage user authentication securely. For authorization, define clear access control policies using role-based access control (RBAC) or account-based access control (ABAC), ensuring that users can only interact with API resources appropriate to their role. Implementing multi-factor authentication (MFA) can add another layer of security, significantly reducing the chance of unauthorized access.

Encrypt Data in Transit and at Rest

Encryption is a necessary practice when it comes to data and information being sent and received by APIs. Encryption converts data into an unreadable format without a key, which is crucial for protecting sensitive information from eavesdroppers. Data in transit refers to data moving across the network, while data at rest is stored on a disk. Both of these states apply to data being transmitted through APIs.

When implementing this best practice, to ensure data is encrypted in transit, use TLS with strong cipher suites. Tools like Let’s Encrypt provide free TLS certificates, helping to streamline this process. For data at rest, apply encryption algorithms like AES and manage the encryption keys securely using managed key services provided by cloud providers or even hardware security modules (HSMs).

Effective Error Handling and Logging

Effective error handling at the code level helps ensure that API errors do not leak sensitive data, while logging records an audit trail of events for later review or real-time analysis. Poor error handling can give attackers clues about the API's internal workings, aiding them in crafting more effective attacks. If attackers can gain access to logs, they could also gain access to private data being logged.

You’ll need to develop a strategy for uniform error responses that conceal implementation details to implement this. Use logging to track and record API transactions, which can help in post-incident analysis and detect patterns indicative of abuse. Ensure any sensitive details are masked or not included in the log output when logging. Tools like ELK Stack or Splunk can aggregate logs for analysis, and cloud services often offer integrated logging solutions.

Use Throttling and Rate Limiting

Throttling and rate limiting control the number of API requests a user can make in a given timeframe. Throttling controls the amount of throughput, queuing API calls that have exceeded the throttle limit so they can still be processed in a controlled, non-spiking manner. Rate limiting is a hard limit that will cut off the API request and return an error response to the API caller. Both of these mechanisms help to prevent service overuse and protect against denial-of-service attacks.

The easiest way to implement throttling and rate limiting is by using API gateways or middleware to manage these rules and policies. When configuring rate limiting and throttling, set sensible defaults based on user behavior and scale them according to your service capacity. These settings can often be adjusted in real-time to respond to observed usage patterns or attacks. Examples of gateways that make this easy include Kong, Tyk, and AWS API Gateway.

Ensure Proper API Versioning and Deprecation Strategies

As time passes, you’ll likely continue improving your API from a performance, functionality, and security perspective. You’ll want to make it easy for your API consumers to understand what version of your API they are using, especially if you’ve improved security on the API endpoint. Versioning allows you to make changes and improvements to your API without disrupting existing clients, while a deprecation strategy provides a planned transition for users from old to new versions.

To implement this, you should adopt a clear versioning strategy, like Semantic Versioning (SemVer), which uses a three-part version number: major, minor, and patch. Once a new version of the API is released, communicate changes through a changelog. If you plan to deprecate older APIs, provide ample warning before deprecating old versions and a path for users to migrate to newer versions. Using tools such as API management platforms can help facilitate the control of different API versions and the smooth transition between them.

Embrace a Zero-Trust Network Model

Another best practice to adopt across all the applications and services you provide, including your APIs, is a zero-trust network model. A zero-trust model operates on the principle that no user or system should be trusted by default, even inside the network perimeter. This is particularly important in modern environments where perimeter defenses alone are insufficient. It gives additional security to services when a perimeter defense has been compromised, limiting the impact of intrusions.

To implement zero-trust, there are a few pieces to put in place. First, enforce strict user verification at every level to ensure users are authenticated and authorized. Next, use the principle of least privilege (PoLP) to ensure that a user or entity only has access to the specific data, resources, and applications needed to complete a specified task. Lastly, apply micro-segmentation to logically divide the data center into distinct security segments, limiting lateral movement. With these pieces in place, you’ll also want to use continuous monitoring and validation at every stage of an API call to ensure that the request is legitimate and that the user still has the right to make that request.

Automate Scanning and Testing for Vulnerabilities

At StackHawk, this best practice hits home the most. Automated and scheduled scanning and testing for vulnerabilities helps to identify potential security issues before attackers can exploit them. By making testing part of the development lifecycle, automation can be put in place to test new pieces of code while it is running, in the case of dynamic application security testing (DAST), or by statically scanning the code, like what you would see with static application security testing (SAST). This proactive measure is essential in maintaining the security posture of your API.

In practice, you’ll want to integrate vulnerability scanning and testing into your CI/CD pipeline using automated tools to analyze your code for known vulnerabilities. Enabling scans and tests to execute on every pull request would be the most comprehensive strategy to find issues early. Use various tools and methods such as DAST and SAST tools to test code for vulnerabilities at runtime, check for outdated libraries or dependencies that may contain unpatched security issues, and other security issues. Regular testing should be part of a broader strategy, including staying informed about new security threats and updating your systems accordingly.

Secure the Underlying Infrastructure

Lastly, ensure that the infrastructure your services are deployed on and rely on is secure. Securing the underlying infrastructure involves safeguarding the physical and virtual environments that host your API. Weaknesses in your security framework here can lead to compromised services, data, and API, undermining all higher-level security measures. Locking down and securing the infrastructure involves server security, network configurations, and cloud environment configurations.

To fortify your infrastructure, ensure that your team has a strict practice of applying regular updates and patches to your servers, enforcing strict firewall rules, and utilizing some intrusion detection systems. In cloud environments, take advantage of native security features and follow the principle of least privilege when setting up access and provisioning user accounts. Also, regularly review your infrastructure for vulnerabilities and consider employing Infrastructure as Code (IaC) for consistent and repeatable deployments, especially when moving from lower to higher environments. Securing each layer of the infrastructure stack creates a strong foundation for building and deploying secure APIs that your users can trust.

We have covered the most critical best practices for securing APIs. Keeping the above in mind, creating a checklist to implement each best practice correctly would be a great place to start. Of course, there may be other factors to consider depending on the types of APIs you have deployed, regulatory requirements, and other factors that make every security framework unique.

Augmenting API Security With StackHawk

As mentioned in our breakdown of best practices, StackHawk is a pivotal tool in reinforcing some of the API security concepts outlined above. By bringing a suite of automated testing capabilities that align closely with best practices for API security, StackHawk is a dynamic application security testing (DAST) tool built for developers. The platform is easy to use, automated, and provides a best-in-class experience for developers to create secure APIs. Let’s look further at some of the benefits StackHawk brings to API developers and their teams. 

Automated Security Risk Tests

StackHawk provides an automated suite to test against common and more advanced API security risks. The platform helps to identify and resolve issues like SQL Injection and Remote OS Command Injection before deployment. This capability supports the abovementioned best practices involving regular security audits and penetration testing.

Integration with CI/CD Pipelines

The platform also integrates easily with CI/CD pipelines and can be set up to ensure every pull request is checked for new vulnerabilities. This ties in nicely with the best practice of testing in development to prevent shipping vulnerabilities to production.

Modern Tooling for Various API Types

Unlike some other tools, StackHawk can support various API types for testing. The tool caters to modern application architectures by supporting REST, GraphQL, SOAP, and gRPC APIs. This helps to ensure that your entire API portfolio has blanket coverage instead of excluding API types that other tools may not support.

Efficient Vulnerability Management

The most powerful outcome for developers that use StackHawk is fast detection and detailed documentation for remediation. StackHawk streamlines the process of fixing vulnerabilities and makes developers' lives easier and the APIs they create more secure. By making the tool developer-friendly, vulnerability management becomes easy to implement and easy for developers to utilize.

By incorporating StackHawk into your API development lifecycle, you can make significant progress towards maintaining a high-security standard and adherence to the best practices outlined in this guide.

Conclusion

As we conclude our in-depth exploration of API security, it's clear that protecting our APIs is critical and complex. Throughout this guide, we've navigated the intricacies of API security, from the foundational principles drawn from the OWASP API Top 10 to the nuanced specifics of securing REST, GraphQL, and gRPC APIs. We capped things off with a look at the strategic best practices that can help fortify your digital defenses and reflected on the importance of each in the broader context of API security.

In the quest for security excellence, tools like StackHawk are indispensable. StackHawk empowers teams to augment their API security strategies effectively. With its automated security testing tailored for modern APIs, integration into CI/CD pipelines for early vulnerability detection, and support for a vast array of API architectures, StackHawk ensures that your security testing evolves with your APIs.

As you look to translate the insights from this guide into actionable security enhancements, consider taking StackHawk for a spin. Begin your journey with StackHawk by signing up for a free account and taking the first step in making your APIs as secure as possible.


Nicole Jones  |  January 2, 2024

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