Best Practices to Ensure API Security: Why and How?

March 12th, 2024 | By Tom Vicary | 10 min read

API security aims to protect API's from attacks and data breaches.

When we use software applications, such as mobile apps, we take it for granted that the information we request will be delivered quickly and clearly. Before this can happen, however, a vital process must occur: the app connects to the internet and sends data to a server, which retrieves that data, interprets it, performs the necessary actions, and sends us what we have requested – all of which happens via an Application Programming Interface (API).

This ability to serve as an intermediary between two software applications so they can exchange data seamlessly means APIs are a foundational element of digital transformation in today’s app-driven business world: they enable mobile experiences, connect companies on the web, and facilitate platform business models.

More than 83% of enterprises use APIs to increase ROI on their digital assets. However, they have become a victim of their success. Their ubiquity (coupled with their ability to enable access to sensitive software functions and data) made them a primary target for cyber-attacks.

Attacks targeting APIs increased an eyewatering 400% in the second half of 2022 – bringing API vulnerabilities and the security best practices needed to mitigate them into sharp focus for businesses. 

Common API security vulnerabilities

Let’s explore five of the most common API vulnerabilities that can lead to network breaches, compromised data, and financial loss for businesses – and provide some tips to help prevent them:

Broken user authentication

This occurs when the user's session ID or credentials have been compromised due to weak API authentication protocols, allowing attackers to take over their accounts, steal their data, or engage in fraudulent transactions.

  • Prevention tip: All authentication endpoints should be protected by strict rate limiting, lockout policies, and weak password checks.

Broken object level authorisation (BOLA)

This occurs when attackers exploit vulnerable API endpoints by manipulating the ID of objects that are listed in API requests. With no check in place to determine ownership of those objects, attackers can access sensitive information by simply changing the ID in a request.

  • Prevention tip: Enforce robust authorization mechanisms and redefine how you generate and manage IDs within your API ecosystem.


This occurs when attackers inject malicious code or commands into APIs through user input fields, allowing them to exploit vulnerabilities or manipulate data. This technique might be effective when APIs do not properly validate or sanitize user input, or when they do not properly handle external data sources or systems.

  • Prevention tip: Validate, sanitize, and/or escape user inputs by performing data validation using a single, trustworthy, and actively maintained library.

Excessive data exposure

This occurs when an application, via an API response, provides too much information to the user – meaning they can’t perform a specific action. This reliance on the client side can expose unfiltered data that an attacker can intercept.

  • Prevention tip: Treat every response and data field as a vulnerability. Review the responses from the API to make sure they contain only legitimate data. 

Lack of rate limiting

This occurs when an API does not limit the number of requests a user or system can make in a given timeframe, which can lead to potential Denial-of-Service (DoS) attacks where a cybercriminal overwhelms the API with requests, causing it to become unresponsive.

  • Prevention tip: Implement a limit on how often a client can call the API within a defined timeframe and notify them when the limit is exceeded. 

What is API security?

APIs' vital role as the backend framework for software systems and services means they are a conduit for sensitive data – including access information, such as authentication and authorization – attracting unwanted attention from cybercriminals.

API security is the process of protecting these backend frameworks from cyber attacks that attempt to exploit them by gaining unauthorized access to the network to steal sensitive data or disrupt services.

Strategies and tools are deployed to restrict access to authorized users only and protect the data transmitted through the API from being compromised or manipulated. 

API security best practices

The widespread use of these business-critical software interfaces has meant their vulnerabilities and the nefarious techniques used to exploit them have expanded the cyber-attack surface. 

To mitigate this threat, and secure their future revenue and growth, businesses must ensure API requests are authenticated, authorized, validated, cleansed, and resilient when the service is under load. This requires the development and implementation of a robust API security strategy that’s built on a foundation of the following best practices.


The first layer of defense against unauthorized access to API resources should be a robust authentication system – using standards such as OAuth 2.0, OpenID Connect, and JSON web tokens – that requires users to provide specific login credentials before gaining access to data. 

This process of thoroughly authenticating all related users and devices typically requires client-side applications to include a token in the API call, allowing the service to validate the client. 


Encrypt all network traffic – notably API requests and responses, as they are likely to contain sensitive data. These communications between APIs and clients should be secured through an SSL connection or TLS encryption protocol like HTTPS.

For maximum security, use the latest and most secure version of HTTPS with TLS 1.3 protocol enabled for all software applications. This will ensure that all data sent between them is encrypted and shielded from malicious third parties.

Access control

Introduce and test controls to manage the level of third-party access to internal data and systems through APIs. This requires a “never trust, always verify” mindset that’s underpinned by three questions: Who? What? When? Known as a zero-trust, this authorization strategy controls data access, creation, update, and deletion.

To reinforce access control, APIs should also be maintained behind a firewall, web application firewall or API gateway – and accessed via a secure protocol – to provide standard protection, such as scanning for injection-based attacks.

Only share necessary information

API responses typically include an entire data record rather than just the relevant fields.

If the client application fails to filter this sensitive data before it’s made publicly available, it not only slows response times; it provides attackers with additional information about the API and the resources it accesses – such as keys, passwords, and other personal information that’s necessary to fulfill a request. For example, if a customer’s age is requested, their date of birth shouldn't be provided in addition.

Record APIs in a registry

You can only secure what you know. To make this possible, record all APIs in a registry to define key characteristics such as name, purpose, and live date. By recording pertinent information, you will be well-placed to meet compliance and audit requirements and assist in forensic analysis in the event of a security incident.

The registry should include all technical API requirements, such as functions, classes, and integration processes.

Assess risks

Conduct a comprehensive risk assessment for APIs in your existing registry that identifies all systems and data that will be impacted if an API is compromised. Use this insight to outline a treatment plan that contains the controls needed to trim risks to an acceptable level. This will empower you to implement measures that ensure compliance with security policies and protection against known vulnerabilities.

To maintain robust security, document review dates and conduct periodic assessments, particularly in response to new threats or API modifications. Thoroughly review this documentation before making subsequent code changes to guarantee the preservation of security and adherence to data-handling requirements.


Keep track of what users are accessing and what they’re doing with that information by continually monitoring your APIs.

Be vigilant by recording every API request and maintaining audit logs of user activity. Robust governance will provide the agility needed to troubleshoot in case of an error and ensure you maintain data security and compliance.

Create and implement a comprehensive auditing and logging policy regularly reviewed and updated to keep up with pervasive cybersecurity threats.


As the backbone of modern applications, APIs create enriching opportunities for businesses to elevate services, engage customers, increase productivity, and maximize profits – but only if they’re secure.

To achieve this, API security must be a systematic process that considers every weak point cybercriminals might target and an ongoing process that keeps pace with the dynamic cyber threat landscape.

Connect with our client-side security experts to know more about it and how to use Jscrambler solutions to protect your client-side assets.


The leader in client-side Web security. With Jscrambler, JavaScript applications become self-defensive and capable of detecting and blocking client-side attacks like Magecart.

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