An Overview of API Security Best Practices

In a tech-driven world, cyberattacks are increasing, thereby businesses need to maintain robust API security as part of their cybersecurity strategy. As for now, APIs can be classified according to protocol, function, and level of access. Based on this, there are different methods to protect sensitive business data. Stay with us and we’ll shed some light on API security best practices, so you’ll take control of attacks in the future. 

What is an API?

Before we focus on API security best practices, let’s get into the question of what an API is and how it works. An application programming interface is a set of programming codes that enable the delivery of data between apps, systems, or servers without user intervention.

Thus, software that needs to access data from another program accesses its application programming interface and defines the requirements for providing data. The other software returns the data requested by the first one. Further, APIs can be called using any programming language or accessed via a webpage opened in the browser. All those ways use architectures like Representational State Transfer (REST) and Simple Object Access Protocol (SOAP) – more below.

However, attackers can hijack API calls and get access to databases. As a result, attackers take over accounts, steal business-critical data and perform service disruption. 

What is API security?

API security is a practice used to protect an application programming interface against various malicious attacks. Moreover, it includes access control and privacy of sensitive data, and identification of attacks in advance.

Typically, application programming interfaces are available over public networks and are very commonly used by attackers. Therefore, organizations must test their APIs regularly to identify vulnerabilities and address them correspondingly. In fact, it is a necessity for any business, and below is why.

Why API security must be a priority

It’s no secret that, with the rise of cyberattacks, insecure APIs pose a serious threat. If their security is insufficient, it will affect users, giving hackers access to their sensitive data. Due to this, a company can have significant financial consequences as well as lose the loyalty of customers.

Therefore, application programming interface security is crucial for their successful and secure operation. But before we move further, let’s focus on the most common issues that companies usually face.

Typical API security risks

Current software systems face a wide range of threats. So, it’s wise to keep updated on the latest vulnerabilities before an attack occurs. To handle this more effectively, let’s review some security risks below:

• Broken object-level authorization: occurs when a request can access (or change) the data that the requestor shouldn’t have access to. For example, the ability to gain access to another user’s account by using a fake ID in a request;
• Broken user authentication: occurs when the process can be compromised and an attacker can pose as another user;
• Broken function-level authorization: occurs when applications cannot restrict confidential functions to authorized users;
• Excess data: occurs when an application (via an API response) returns more data than is relevant for a user to perform a specific action;
• Security misconfiguration: occurs when essential security settings are not implemented or have errors that create dangerous gaps;
• Injections: occurs when hackers inject malicious elements into web applications, which are then unsafely processed.

API security best practices

Each company implements application programming interface security in a different manner. However, there is a set of best practices that can be applicable to any organization.

Authentication and authorization

For APIs to be secure, authentication and authorization are equally important. Authentication deals with verifying the user’s identity. While authorization focuses on what the authorized user has access to. But together, they ensure that the right user can use the API to access the data at different levels. 

Therefore, to assure reliable access to application programming interface resources, companies need to establish solid authentication and authorization controls. Let’s look at the most effective ones:

• Access tokens: each API key has a unique identifier for each user and each authentication attempt;
• HTTP basic authentication: relies on local usernames and passwords;
• OAuth with OpenID: allows users to access corporate resources by determining their authorization. Together, OAuth and OpenID provide authentication and authorization;
• JSON web token (JBT): is used to implement key-based client authentication and to transfer information between parties (using JSON format).

Overall, these four methods enable companies to define access control rules and provide the security they need without losing the ease of API management.

Select the web services API

There are two main ways to access web services via APIs. The first way is by using the Simple Object Access Protocol (SOAP) – a highly structured message protocol that supports several low-level protocols. The second way is by using the Representational State Transfer API (REST API) based on a set of architectural principles.

Both of them support HTTP requests, responses, and the Secure Sockets Layer (SSL) protocol, but this is where the similarities end. SOAP and REST APIs use different formats and require different strategies to ensure robust security. Now, let’s look at each of them in depth:

REST API:

• Compatible with various data formats like HTML, XML, and especially JSON;
• Doesn’t support WS web-services specification, including SW-Security; 
• Lack of built-in security capabilities;
• Security depends on the API design or gateway; 
• Provides access to data, so it’s a simpler way to access web services. 

SOAP API:

• Compatible only with XML;
• Has built-in security capabilities based on W3S and OASIS recommendations;
• Supports Web Services (WS) specifications, which provide enterprise-grade security for web services;
• Supports WS-Reliable Messaging, which provides built-in security capabilities;
• Complex to implement and may require refactoring of an app.

In sum, SOAP APIs are more secure by design, but REST API security best practices allow to make it highly secure, depending on their implementation and the architecture you choose.

Keep in mind:

Assess your risks

Performing a risk assessment is another effective security practice. Early on, we’ve written about top risks you should be aware of. Therefore, the next step should be to establish proper security measures to prevent those risks. To perform a risk assessment, a company needs to pay attention to the following:

• Determine the risk assessment: you need to determine what is in the scope of the evaluation (a business unit, or a specific aspect of the business, like a web app) by using standards like ISO/IEC 2700;
• Identify threats: threat actors use tactics, techniques, and methods that can harm an organization’s assets;
• Analyze risks and their potential impact: identify risks and their impact on an organization;
• A company can prioritize risks: by using a risk matrix that categorizes each risk. To achieve a successful security strategy, stakeholders need to accept residual risk;
• Document risks: keep a safety risk register so that the company can review it regularly and update it as necessary.

It is necessary to repeat the assessment because cyber threats continue to grow, and companies need to constantly adopt updated technology systems. A successful risk assessment set up a repeatable process and patterns for future assessments. Thus, having a risk assessment will allow a security team to make informed decisions about how and where to put in place security controls.

Validation of the data

There are times when legitimate requests may be hacking attempts. Therefore, APIs need to determine whether requests are friendly or harmful. For that, validation is a perfect solution. 

Being part of the development process, validation is able to check that an application programming interface meets expectations of functionality, performance, security, and other quality attributes. In general, the validation process is carried out in one of the following ways:

• Static analysis: a manual examination of API code for vulnerabilities;
• Dynamic analysis: observing how an API works to find security flaws;
• Fuzz testing: testing an API’s response after sending any data to identify potential vulnerabilities. 

In order to validate APIs, a company needs a specification that describes how the application programming interface should work. However, a business may consider the OpenAPI Specification (OAS), which defines APIs and API contracts. As a result, validation helps to track errors and improve user experience.

Encryption

Encryption is a basic element of security. Yes, you’re not wrong if you think so. Indeed, the use of encryption makes the clear text unreadable, thereby making it more difficult to compromise sensitive information.

To prevent any attacks, the transmission of data from the user to the API server must be properly encrypted. There are strong encryption methods, such as Transport Layer Security (TLS) and Secure Sockets Layer (SSL). Companies may use these protocols to encrypt web pages and REST API.

As well, some CRM platforms that companies use may provide free SSL encryption. But if your platform does not offer SSL, you will need to implement one through an API or plugin. As a result of this process, your APIs are protected. Therefore, an attacker will not be able to access intercepted requests or responses.

Conduct regular security tests

It is not a good idea to wait for a real attack in order to check how secure your defenses are. Instead, you need to find time to test your security in advance. Security tests involve intentionally hacking into your application programming interface to discover vulnerabilities. On top of that, your API should be tested regularly, especially when it is updated. Let’s move on to how to complete the testing process.

The first step is to ensure that your API is working as expected. In other words, you would submit normal requests via an API client while adhering to the principles above. When you’ve established that your application programming interface is working well, the second step is to simulate attack scenarios like injection, DoS, or stolen passwords against your systems. Here are a few tests a company can run:

• User authentication: send requests without proper authentication and see if your API returns the correct error message;
• Parameter tampering: use invalid query parameters in API requests and see if it responds with the correct error codes. If the answer is no, your API likely has some validation errors;
• Injection: try injecting SQL, OS, or other commands into API inputs and see if your API executes them;
• Unhandled HTTP methods: try all the common HTTP methods as well as a few uncommon ones. Try sending a request with HEAD instead of GET. As a result, you should get an error code, but if not, there is a vulnerability.

Also, keep track of:

Use TLS

One way to secure your application programming interface is to ensure that it uses TLS (Transport Layer Security). During transit, TLS encrypts the information that your API sends. When a website’s URL begins with HTTPS: instead of HTTP: that means it is using TLS. With TLS, a third party will not be able to intercept and read sensitive information during the transmission of, let’s say, private data or API credentials.

Pay attention to the fact that TLS requires a certificate, which provides legitimacy and protection for your API. Most cloud providers and hosting services will manage your certificates. It sounds convenient because providers will automatically secure every API call instead of you. In addition, if you’re running your web server without any third-party services, you’ll need to manage your own certificates. 

Manage firewalling

With API Gateway Manager, companies can track API firewalling on API Gateway interfaces. API Gateway provides a toolkit for real-time HTTP traffic monitoring, logging, and access control. In this way, companies can mitigate application-level API threats. In order to ensure API security, you should organize it into two levels:

• DMZ: the first level with an API firewall to stop intruders as early as possible (for example, SQL injections);
• LAN: the second level of security, ensuring better data security.

Share data as little as possible

The last among API security best practices is to avoid “oversharing” data. It’s not about being overly protective and hiding all the data. It means being overly cautious when you protect sensitive data.

API responses often contain a lot of data and may give attackers extra information. To prevent various attacks, all API responses must include data about the transmission of the requested resource or data directly related to those resources. In a nutshell, responses should contain the minimum information that is necessary.

Companies need to avoid having too much unnecessary data transfer that can expose private data. This, in turn, will provide better API security. Alternatively, organizations can use IP Whitelists or Blacklists, if possible, you can also limit access to resources. If you can limit the number of administrators or delimit access for different roles, you can maintain the interface securely.

Final thoughts 

Obviously, the proper use of application programming interface provides a tremendous amount of opportunities to a business. But there is no doubt that it’s easy to get it wrong when it comes to security. As a result, a company may be exposed to serious threats. Although it is impossible to eliminate all threats, the above API security best practices are essential for any organization which cares about its brand and, primarily, about its customers.