What to Know For Better API Security Beyond the Design Phase

Isla Sibanda
by Isla Sibanda on February 28, 2023 7 min read

Application programming interfaces (APIs) present a range of specific security issues that present significant risks if left unresolved. APIs process large quantities of data relating to a wide range of functions, representing a considerable portion of all internet usage. This is why they are commonly targeted by cybercriminals.

Security measures such as API management tools and API gateways have their uses, of course, but they are not designed to prevent cyber attacks which target often unknown vulnerabilities. This means they are looking for areas to exploit that are not taken into account during standard scanning and testing.

In this article, we will look at what you need to know for better API security, helping you to protect against potential attacks during both the development and testing stages of API production.

Why API Security is Vital

APIs are effectively the building blocks of all modern software applications and need to be fully protected. API security is vital, but it is also very challenging as one API can be completely different from another, meaning there is no one-size fits all solution. In addition to this, APIs are also constantly evolving, closely following changes in the software development world and advancements in technology. These changes can happen so quickly that keeping track of them and documenting them sufficiently proves almost impossible.

Despite these difficulties, maintaining up-to-date and accurate documentation is essential when it comes to API security, helping security teams share intelligence and mitigate risk.

Many existing API security solutions, such as API gateways and standard management tools are not built to prevent attacks. In any case, most attacks target unknown vulnerabilities that standard solutions are not checking for. The purpose of these attacks can vary, from attempting to fully take over accounts to obtaining login credentials and API keys.

Should an attack of this sort be successful, then the consequences to an organization can be sometimes irreparable, possibly resulting in a breach of their customer’s data and compromising the integrity of their brand.

Implementing API Security

As discussed in the previous section, securing an API presents multiple challenges and requires more expertise than standard software security. The fundamental software security principles still apply to APIs but they alone cannot provide a comprehensive solution.

To effectively protect APIs from an attack during their development, testing, and production, a combination of expert knowledge and ongoing education is needed. By applying this knowledge, API security can prove no more of a test than any other type of software security, in principle.

We already know API security is essential in the design phase of your API creation, which you can read about here. But where else in the lifecycle stages do we see security playing a crucial role? Read on to find out!

Phase 1: API Security During Development and Testing

The coding and configuration process during software development is one of the most vulnerable stages of an API’s lifecycle which is why security needs to be implemented from day one. Consider seeking the services of an experienced developer who can assist you with security during the development and testing cycle.

Building security protocols and encryptions is a core task that any developer you hire should know. You can expect to pay somewhere between $60-100 per hour for an experienced freelance developer who understands security, which should be cheaper than going with a third-party agency. An experienced developer will likely be adept at creating code that is completely secure; however, when it comes to APIs, additional resources should be utilized to ensure maximum security.

1. Streamlined Data

The first consideration is to make sure that the API only sends information that is required, and nothing more, as too much data exposure presents opportunities to cyber criminals. By failing to manage what data is transmitted by the API, attackers can often bypass the client application and hijack these data transmissions to gain access to a range of sensitive information. This is one of the most commonly executed attacks on APIs.

Limiting the amount of data transmitted by the API is especially important for clients in the financial and banking sector who need to adhere to PCI compliance and other regulations. The PCI-DSS standards are a set of requirements established to ensure the security of payment card transactions between customers and businesses.

Many tech-savvy users pay close attention to how data is collected and used and are likely to only use software or applications that they know have strong documentation and security features.

In terms of protecting their finances, most consumers only consider business bank accounts that come with security features such as real-time account monitoring and multi-factor authentication. A recent study revealed that over 40% of respondents prefer to exclusively use online banks for their banking needs. Ensuring that online banking applications are not just user-friendly but also secure is essential to winning over consumer trust.

2. Good Documentation

Secondly, documentation is one of the most crucial aspects when it comes to API security. This documentation needs to be regularly maintained so it is up-to-date and accurate, containing in-depth information regarding how the API was developed and integrated, so it is available at all times.

The documentation should contain elements such as design reviews and findings from security tests. Any inaccurate or outdated information could result in vulnerabilities being missed during penetration testing or regular security checks. To ensure accuracy, APIs can be documented using the OpenAPI Specification (OAS) which provides a standardized format and defined structure, making documenting an API much more efficient.

3. API Inventories

Detailed API inventories should also be recorded on a regular basis, helping security teams have a complete understanding of the API’s overall attack surface. API monitoring tools can help to detect different API formats automatically, helping to give security teams an overview of formats they may not be familiar with.

4. Design Reviews

Finally, design reviews are crucial when developing any software product, especially APIs. These reviews or evaluations ensure that the API is being suitably developed for its intended purpose, highlighting any deviations and potential flaws in the design. By identifying these issues early on in an API’s life, they can be quickly resolved or improved with minimal impact.

Business logic should be used when conducting a design review, as many scanner tools fail to detect vulnerabilities that could be exploited by attackers. Security testing tools should also be deployed to identify any configuration problems and check for known vulnerabilities. This is typically followed by fuzz testing to find any discrepancies in the source code and then the scheduling of automated monitoring and analysis.

Phase 2: During Runtime Protection

Development and testing are only the first stages of API security; in fact, the runtime protection of the product could be considered even more important. The key aspects of runtime protection are dynamic discovery and the detection and prevention of an attack.

Runtime protection tools should also detect any API misconfiguration issues within its infrastructure and analyze behaviors, checking for exploits such as brute force attacks and credential stuffing.

1. Monitoring Behavior

This is achieved using tools that can measure typical user and API behaviors so any anomalies can be spotted easily. The analysis provided by monitoring tools can also be crosschecked against documentation to identify any unusual activities or irregularities. Again, this reaffirms the need for documentation that is current and accurate in terms of normal behaviors.

2. Authentication

Setting up continuous authentication is also essential when protecting an API against potential attackers. This requires Identification and Access management tools, public key infrastructure, and API key management.

Authentication and authorization best practices include:

  • Keeping all identity keys and access controls on a separate database
  • Do not use API keys as a method of authentication
  • Use multi-factor authentication to provide additional layers of security


In summary, the challenge of enhancing API security can be mitigated by following core security principles, using the correct tools, conducting regular testing, and keeping thorough, current, and accurate documentation. The effectiveness of any API security strategy is also strengthened by conducting inventories and design reviews during the development stage, and by monitoring user and API behaviors during runtime.

The good news is that adhering to these security fundamentals can ensure API security is no more of a challenge than any other type of software security. We always say that shifting left on your security practices helps a ton, but these are some good first steps!

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