8 Inspiring Best Practices for API Security

To make data unreadable to third parties, encryption is ideal. Generally, a distinction is made between two different forms of encryption, namely encryption at the transport level and at the message level. 

In transport level encryption, the API uses an encrypted network connection to exchange data. This prevents man-in-the-middle attacks in which a hacker listens in on the messages being exchanged between the client and the API. To achieve this, we use Transport Layer Security (TLS) with security certificates issued by a recognised authority.

All the previous applications of encryption are already considered quite standard, but we also recommend message level encryption. This is especially interesting when you are working with sensitive data, such as medical records, financial information, and other personal information to which GDPR legislation applies. In this case, organisations (e.g., hospitals, financial institutions, etc.) can choose to encrypt the content of the messages themselves. This ensures that the data being stored is only readable by those who have the corresponding key to decrypt the data. 

Software such as a Web Application Firewall or an API Gateway protects against many threats. However, the security world does not stand still; on the contrary, everything is evolving rapidly - new threats are constantly being discovered that companies need to protect themselves against. It is a fact that encryption keys considered secure today may not be so tomorrow. Therefore, it is crucial to always install the latest security updates and patches in your organisation. 
 
We also recommend having your API audited at least once a year with an API security audit. Regular audits are necessary because new methods are continually being discovered to disrupt organisations' APIs. In such an audit, the current solutions used within the organisation are first examined. A maturity level in terms of API security is determined, taking into account the future integration capacity needed to support the business. Based on this, recommendations are formulated for addressing security issues related to API architecture, technology, and organisation.

It is important to closely monitor the use of your organisation's APIs. A systematic approach through automation is strongly preferred. An attack by a hacker may potentially be stopped by the Web Application Firewall or API Gateway, but if that attack goes undetected, it gives the hacker more time to prepare their next attack. With good monitoring, you can recognise attack attempts and prevent the attacker from trying new attacks, for example through IP blacklisting. 
 
AI and machine learning can now also recognise certain patterns of a potential attack. This allows for automatic protective measures to be taken.

During API design, it is important to carefully consider which data you decide to make available via the API. This is not only about which fields you add to the response, but also about avoiding situations where a client can request data from another party by modifying the input parameters of the request. 
 
A high-quality API design tool allows you to see what the API will effectively return in its response. This gives you a quick and easy overview of areas where improvements may still be possible. The truly advanced tools also proactively prevent design mistakes and predict the possible impact of those on the operation of your API.

When an API returns a response to a client, it can include certain parameters in the HTTP response headers. These parameters prevent clients from carrying out actions that could be part of an attack. Examples of such parameters are enforcing an HTTPS connection (HSTS), preventing cross-site scripting (XSS), and avoiding content-type sniffing.
 
For the selection and use of security headers, it is best to be guided by an expert in this area. Incorrect usage can allow hackers access to, for example, cross-site scripting (XSS) or content-type sniffing. 

When your API allows a list of inputs but you do not limit the size of that list, it can cause a very large load on your backend applications. Therefore, it is important to use strict validation rules that prevent such exceptional input values from reaching your backend in the first place.

Shadow APIs are unprotected APIs that often lead to significant breaches and outages in software systems. They provide malicious actors with easy access to sensitive data and can cause damage by inadvertently granting access to private user accounts and making unwanted changes to user information. To identify shadow APIs, monitoring, log analysis, and code scans can be applied. It is important to implement strict standards and guidelines within the organization and to use tools to effectively combat shadow APIs.
Also consider seeking guidance in optimising and professionalising your organisation's API architecture. One of the options commonly suggested is to establish a Centre of Excellence (CoE). This is a central governance structure aimed at ensuring the quality of integration solutions and continuously improving it. 

API authentication is the process of verifying the identity of users who want to access an API. It is crucial to ensure the security of APIs and prevent unauthorized access. There are various best practices for API authentication. One of them is the use of tokens, such as OAuth tokens, to verify the identity of users. It is also important to use HTTPS (TLS) to encrypt communication with the API and protect sensitive information. Finally, it is recommended to implement a strong password policy, such as requiring complex passwords and implementing mechanisms like multi-factor authentication to add extra layers of security to the API's authentication process.

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