With growing digital businesses and continuous evolution in the software and IT industry through Micro-Services Architectures, APIs Security is becoming a prime focus and API Security Best Practices have become a mandatory requirement to safeguard any organization’s digital assets.
In this article, 8 Best Practices for Securing APIs are discussed in detail.

Why API Security is So Important?

APIs open a door to the business and its digital assets and capabilities in the form of API operations. When you open a door, security becomes your major concern as you want to ensure that no intruders can pass through the doors to misuse your assets. With technological evolutions, threats are also increasing as attackers are clever enough to find their ways by exploiting the vulnerabilities in the API design and underlying infrastructure weaknesses.

APIs need to be designed and implemented by keeping latest security threats in mind and by ensuring that all standards and best practices are being followed in order to have Secure, resilient and reliable APIs exposed to the intended audience.

Lack of Security features in the APIs can potentially cause severe business losses, data breach, data anomalies, infra-structure mis-use and potential legal consequences if personal data is compromised in any form.

API Security Best Practices

When designing and implementing APIs, Security related Best Practices must be followed to deal with potential security threats and to safeguard digital assets and to serve legitimate API consumers in an efficient and secure manner.

Below we will shed a light on 8 API Security Best Practices.

Encrypt Data to Avoid Data Breach: Both Transport Level and Data Level

Data should never be transmitted over the network in a naked fashion and its integrity, confidentiality must be ensured through encryption mechanism. At transport level, SSL with strong ciphers should be enforced to have a secure and reliable data transfer so that Man in the Middle Attacks can be avoided.
When integrating through APIs, commonly One Way SSL is used which is sufficient to achieve desired goals of transport level encryption. However, for B2B scenarios, Two Way SSL also known as Mutual SSL is also used where both client and server sides need to trust each other through certificates. I have explained in another post about Difference Between One Way and Two Way SSL.

Apart from Transport Layer security, data encryption is also recommended at the data/payload level for critical business scenarios. E.g. if you are working with APIs in banking/financial domain, It is recommended to apply encryption/hashing mechanism at the payload level as well which will add another level of data security.

Configure Authentication & Authorization: Who can Access, What can be Accessed

APIs must be secured through Authentication Mechanism and only authenticated calls should be permitted to pass through. For Authentication, different types of authentication schemes can be used as per requirement. The least recommended approach is Basic Authentication where Username and Password in the request header with Base64 encoding are used to authenticate. Another approach is to use API Keys as Opaque tokens. However, the recommended approach is to use OAuth for a better security.

It is also important that when tokens are used, those should be short-lived to avoid token compromises. Tokens issuance, refresh, revoke endpoints should be used in a secure manner for such requirements.

While Authentication tells who can access an API, Authorization tells which resources or operations can be accessed. It is important that you protect and secure your digital assets (data) by enabling Authorization so that consumers are able to get only what they are entitled to and nothing less, nothing more !

Role based Authorization is a common approach and a best practice for API Security. Users/Clients need to be categorized as per roles and access scopes need to be defined as per role. E.g. a client with the role of HR might be given access to confidential payroll data under Employee API but another user with Staff Role might have access to same Employee API but not able to invoke operations related to payroll.

No Entry for Invalid Requests: Validate All Requests/Data First

APIs are a door to the backend and this door must be safeguarded against any invalid data to avoid data inconsistencies and anomalies in the backend systems. Data must be validated against generic validation rules before passing it to the next stage.

Use of Enumerations, Regular Expressions at Schema Level can help identifying invalid requests and such technical validations at the API level can help filtering requests before reaching backend systems.

Hide Internal Details: Send Custom Error Messages

For attackers with malafide intentions; the best gift that they can have is an exposure of the internal technical details of your systems. With such information exposed; it opens doors to potential threats as such attackers can devise better strategies to benefit from your system’s vulnerabilities. It is always recommended that internal technicalities of your APIs implementation and underlying systems should never be exposed when returning API responses in happy as well as un-happy scenarios.

Ensure that all technical issues are kept limited to your own implementation boundaries and custom–generic error messages should be returned back in case of any errors or failures. Returning Stack traces or technical error details is a bad practice and must be avoided.

Share Only What’s required: Limit Details in Response Carefully

Data is always precious as well as critical depending on the business. When exposing APIs for your consumers, data should be shared with utmost care and nothing confidential or irrelevant should be made available to the clients. For example, if you have exposed a GET API to allow consumers to retrieve product information; any secret or private details about the product, its composition shouldn’t be returned back and only relevant and necessary information must be made available. It is never recommended to map your Payloads directly to a data Table in the backend database.

Secure Using API Management Platforms at Gateway Levels

API Management Platforms are highly recommended to better control, manage, monitor and monetize your APIs and underlying digital assets. From security perspective, API Management Platforms provide you a rich set of Policies which you can enforce at API Gateway level. E.g. you can have policies for throttling, rate-limiting, Scope based Access Control, Different types of authentication schemes, IP Blacklisting/Whitelisting policies etc. at API Gateway Level.

API Management Platforms help you to decouple API implementation from API Management and helps you to have a better control and governance for your APIs with an added layer of security and control.

Recommended: Video Tutorials About APIs and API Management

Analyze, Monitor Traffic Behaviors to take pre-emptive and corrective actions

APIs usage statistics, Consumers Behaviors and APIs performance must be regularly analyzed and monitored to ensure that APIs are working as desired and no abnormal behaviors are present in terms of APIs invocations, Subscriptions, Throughput etc.
Using API Analytics provided by API Management Platforms, you can have a graphical and detailed insight into your APIs usage patterns and that can really help you to take any pre-emptive and/or corrective actions to keep your API Eco-System secure and efficient.

Keep yourself and your APIs updated with latest security threats

APIs secured today might not be in a secure status tomorrow as new threats, new vulnerabilities are regularly getting identified and it is extremely important that you must keep yourself up-to-date with latest security threats and resolutions. Your API Management Platforms, API Implementations and Backend Systems must be kept updated with latest security patches and security recommendations from the vendors.

It is also important to regularly perform security assessment for your APIs and underlying systems to deal with vulnerabilities in a timely manner.