What Is API Security? Complete Guide & Best Practices

APIs (Application Programming Interfaces) are the backbone of modern applications and services. With their help, various systems communicate and exchange information. Whether it’s a mobile app fetching data from a server or a third-party service integrating with your software, APIs are critical in enabling these connections. 

As the reliance on APIs grows, so does the risk of related security breaches and other vulnerabilities. Processing sensitive data means it can be exposed if mishandled, making APIs a prime target for attackers. 

In this guide, we’ll break down the nuances of API protection. Learn about the common risks associated with APIs, explore the core standards, and discover the best practices to secure them. Drawing from Iterasec five years of hands-on experience tackling all aspects of API security, dive deep into this article to uncover expert cybersecurity strategies.

What Is API Security?

API security is about protecting the heart of your digital operations. Specifically, this term describes the practices and measures to protect APIs from attacks by ensuring only authorized access, preventing data breaches, and safeguarding the integrity and confidentiality of communication between systems. 

API cybersecurity ensures that only authorized users can access and manipulate data through gateways between different software parts and systems. It also involves securing the transmitted data (ensuring confidentiality, integrity, and availability) and verifying that the API behaves as expected, even under attack. 

Securing an API protects the systems that interact and the data exchanged. From a business perspective, it prevents breaches, system disruptions, and financial losses.

Why API Security Is Important

Security is among the primary factors promoting trust in your products and services. For APIs, security is vital for several reasons related to their nature:

1. APIs often handle sensitive data. It includes personal information, financial details, proprietary business logic, and so on. 
2. APIs are the glue binding the majority of modern applications. A compromised API can be an entry point for attackers to infiltrate your entire system. 
3. Regulatory compliance mandates strong security practices. Industries like healthcare and finance have strict rules about data protection. 

Neglecting API security may result in a breach. It leads to data loss, financial repercussions, and reputational damage. Hackers can disrupt services or hold your business hostage with ransomware. Even if everything is fine, failing to secure your APIs could result in hefty fines and legal troubles.

Given how widespread APIs are, companies are facing an expansive potential attack surface. APIs link digital products with third-party software, IoT devices, and internal systems. Without proper security measures, each connection becomes a vulnerable point.

API insecurity costs $12-23 billion annually in the US and $41-75 billion globally. These are mainly avoidable losses. The study shows a positive correlation between company revenue and the frequency of API-related incidents.

API security management safeguards your data, users, and business simultaneously. It also reduces the attack surface. It minimizes risks and prepares your firm for a potential security crisis.

Common API Security Risks

The risks arise from how APIs are designed, implemented, and managed. The list of potential threats and issues includes more than several problems. However, these are well-studied and common risks. If your security team understands the typical risks, it prepares to prevent them.

The most widespread API cybersecurity risks, vulnerabilities and attack types include the following:

• Broken authentication. Missing, weak, or improperly implemented authentication mechanisms result in unauthorized API access.
• Authorization flaws. Inadequate authorization mechanisms provide users with data they shouldn’t access and let them perform unauthorized actions.
• Injection attacks. APIs that don’t correctly validate and sanitize input are vulnerable to injections. Hackers may input malicious code into an API to manipulate it.
• Insecure endpoints. Endpoints lacking encryption or proper security controls are vulnerable to man-in-the-middle (MitM) attacks. Hackers intercept and alter communication between the API and its users.
• Excessive data exposure. APIs that return more data than necessary may share sensitive information with those who shouldn’t see it. 
• Rate limiting and throttling issues. The lack of throttling and rate limits leaves APIs vulnerable to denial-of-service (DDoS) and bot attacks. Hackers overwhelm an API with traffic, aiming to make it unavailable. 
• Insufficient input validation. Failing to validate input data makes APIs unprotected against attacks like buffer overflows or cross-site scripting (XSS).
• Security misconfigurations. Incorrect settings or defaults may also occur, leaving APIs at risk of cyber-attacks.

Keeping software components that APIs rely on updated is also critical. Outdated software is often vulnerable to known exploits by evildoers. Finally, remember about proper issue logging and monitoring. Without them, malicious activities targeting the API go undetected. As a result, attackers exploit vulnerabilities over an extended period.

API Security Standards

API security standards are guidelines designed to help organizations protect their APIs. These are frameworks for ensuring security, reliability, and compliance with industry regulations. 

For example, OWASP API Security Top 10 is a recognized standard that outlines the most typical API security risks. It provides a clear understanding of the vulnerabilities, featuring the ten most common threats:

1. Broken Object Level Authorization (BOLA)
2. Broken Authentication
3. Broken Object Property Level Authorization
4. Unrestricted Resource Consumption
5. Broken Function Level Authorization
6. Unrestricted Access to Sensitive Business Flows
7. Server-Side Request Forgery (SSRF)
8. Security Misconfiguration
9. Improper Inventory Management
10. Unsafe Consumption of APIs

Some other widely used standards are:

• OAuth 2.0 – an authorization framework that enables applications to access protected resources on behalf of users securely
• OpenID Connect – an authentication protocol that provides a standardized, simple, and secure way to verify user identities
• JSON Web Tokens (JWT) – an open standard that secures the transmission of information between parties as JSON objects
• Transport-Layer Security (TLS) – a cryptographic protocol that encrypts the data transmitted between the client and the API

Some general guidelines also consider API security standards. For example, ISO/IEC 27001 isn’t specific to APIs. It’s an international standard for information security management that covers all aspects of an organization’s information security, including API data security.

Types of APIs and Their Security Considerations

APIs come in various forms. Each serves a different purpose and requires specific security considerations. In a broader sense, the three main types of APIs are: 

• Public (open) APIs are accessible to anyone with an API key.
• Partner APIs are accessible to specific partners or organizations.
• Private APIs are for internal use only within an organization.

Public APIs, being widely accessible, are particularly vulnerable to attacks. Partner APIs require careful management of trust and data sharing. Finally, private APIs are less exposed. Still, even they require robust security measures to protect sensitive internal data.

It’s also possible to classify APIs based on their tech stack and implementation capabilities. The security principles apply to all these types differently. However, each has its specific protection considerations.

REST API Security

REST stands for Representational State Transfer. These APIs are popular due to their simplicity and scalability. REST APIs rely on standard HTTP methods. They use commands like GET, POST, or DELETE to perform operations. 

REST APIs are stateless and typically communicate via JSON. It makes them lightweight and easy to use. When inspecting REST API security, focus on the following aspects: 

• Authentication and authorization. Implementing OAuth 2.0 is a standard practice for securing REST APIs. JSON Web Tokens are also a popular choice for managing user sessions securely.
• TLS encryption. Encrypting data in transit with TLS is essential to protect against eavesdropping and MitM attacks.
• Rate limiting. REST APIs should enforce rate limiting to prevent abuse. It restricts user or client’s requests within a certain period.
• Input Validation: REST APIs are vulnerable to injection attacks. Validating and sanitizing all input data is crucial.

SOAP API Security

SOAP (Simple Object Access Protocol) APIs are distinctive because of their robustness and strict standards. They use XML for message formatting and operate over various protocols (HTTP, SMTP, etc.). 

Enterprises often use SOAP APIs where security and reliability are paramount. The primary considerations for this type of API are the following: 

• WS-Security. It’s an extension for SOAP. This standard provides message integrity, confidentiality, and authentication. WS-Security relies on mechanisms like XML Signature and XML Encryption.
• SSL/TLS. Secure Sockets Layer and Transport Layer Security are cryptographic protocols that ensure safe communications. SOAP APIs should use SSL/TLS to secure communication channels, guaranteeing data encryption during transit.
• Message-level security. SOAP encrypts and signs each message independently. It provides a higher level of protection compared to transport-layer security alone.
• Complex security configurations. SOAP’s security features are more complex and configurable than REST, which is both an advantage and a challenge. It’s critical to implement these APIs carefully and avoid misconfigurations.

GraphQL API Security

GraphQL is another query language, a more flexible alternative to REST. With its help, clients request the data they need, potentially from multiple sources in a single query. As always, such flexibility introduces unique security challenges.

Here are the most significant security considerations regarding GraphQL: 

• Query complexity control. GraphQL APIs are sensitive to overly complex queries that overload the server. Implementing query complexity analysis and rate limiting can prevent this outcome.
• Authorization. Advanced access control is essential in GraphQL. Ensuring users can only access the authorized data that involves implementing custom logic.
• Introspection queries. Introspection queries are helpful for developers but expose API structure to attackers. It’s essential to control or disable these queries in production environments.
• Input validation and sanitization. GraphQL APIs must validate and sanitize all user inputs to prevent injection attacks. It’s critical since GraphQL involves highly dynamic queries.

REST API Security vs. SOAP Security

REST and SOAP APIs are the ones used most frequently. They differ in architectural style, design, and security approaches.

REST APIs are more lightweight and easier to implement. However, this simplicity comes at the cost of less built-in security. REST relies heavily on Transport Layer Security (TLS) and external authentication and authorization standards. It’s more prone to particular security vulnerabilities, such as access controls and authorization issues, if not adequately secured.

SOAP APIs include built-in security standards. For example, WS-Security provides more granular control over message-level protection. It makes SOAP a preferred choice for companies in the financial or healthcare sector, where security is paramount. However, the complexity of SOAP configurations requires more expertise to implement them correctly.

Therefore, REST APIs are more straightforward and secure due to their stateless nature and reliance on standard HTTP methods. In contrast, SOAP APIs provide a comprehensive security framework but are more complex to implement and manage. 

While SOAP APIs include security standards like WS-Security, these mechanisms don’t inherently make SOAP more secure. In fact, SOAP is vulnerable to many of the same security risks as other API protocols, such as XML injection, broken authentication, and misconfigurations. WS-Security provides granular message-level protection, but its complexity and the need for expertise in configuration often lead to implementation errors that can introduce vulnerabilities.

On the other hand, REST APIs, which leverage HTTP protocols, are simpler to implement and secure. Their stateless nature and the widespread use of industry-standard security measures such as OAuth or HTTPS make them more adaptable. While SOAP APIs offer a broader security framework, they are harder to manage and are not inherently safer than REST APIs. Both protocols require careful security practices to ensure protection.

The choice between REST and SOAP depends on your business needs. Consider the application’s specific requirements, the required security level, and the development team’s expertise when selecting an API. After deciding on one, explore all the nuances and build the security strategy accordingly. 

API Security Best Practices

So, how to secure APIs? Best practices are always combined and configured specifically for each business and software system. Below, you’ll find several tried-and-true tips you can treat as the basic rules for securing any API.

Use Strong Authentication Methods

Authentication is the first line of defense in API security controls. Prevent credential stuffing and ensure that only legitimate users and systems can access your APIs. Weak or improper authentication leaves APIs vulnerable to unauthorized access and exploitation. Mechanisms to prevent those include the following:

• Verified industry standards like OAuth 2.0 and OpenID Connect.
• Authentication tokens to verify the identity of a user or system interacting with an API
• Multi-factor authentication, which requires an additional code or biometric scan in addition to a password
• Strong password policies with a combination of uppercase and lowercase letters, numbers, and symbols 
• JSON Web Tokens for secure and scalable session management

Implement Role-Based Access Control (RBAC)

RBAC regulates access to APIs based on user roles. With its help, you limit access to selected resources, leaving them accessible only to specific users. It reduces the risk of unauthorized actions. To enable effective RBAC, take the following steps:

• Clearly define the different roles and permissions for each.
• Grant users only the minimum necessary permissions.
• Strengthen with attribute-based access control (location or device alongside the role).

API Key Management and Rotation

Proper API key management helps prevent unauthorized access and limits the potential for misuse:

• Use unique API keys for each service or user.
• Regularly rotate API keys to reduce the risk of compromised keys.
• Enforce expiration policies for keys and automatically invalidate unused keys.
• Monitor the usage of API keys and set up alerts for any suspicious activity.

Encrypt Data

Encryption is a fundamental security practice. It protects sensitive information transmitted through your APIs. Moreover, it keeps data “unreadable” even if someone unauthorized accesses it. To secure APIs to the maximum, follow these practices: 

• Encrypt data at rest (stored on disk or in databases).
• Encrypt data in transit (transmitted over the network).
• Put secure key management practices in place to protect encryption keys.

Use API Gateways

API gateways act as intermediaries between clients and your APIs. Consider them a single point of entry for all API traffic. With gateways, you enforce security policies and monitor usage. Such a point puts solid security measures in place—but only when used correctly. Here’s how to adopt API gateways appropriately: 

• Use the API gateway to handle all authentication and authorization processes.
• Utilize built-in security features for authentication, authorization, and data validation.
• Implement rate limiting to prevent excessive API usage.
• Adopt quotas to restrict the overall usage of API resources.

Secure API Endpoints

Protecting the entry points through which clients interact with your API is vital. Exposed or poorly secured endpoints are vulnerabilities, welcoming attackers to exploit them. Here are several essential tips on securing the endpoints: 

• Ensure all API endpoints are only accessible via HTTPS. 
• Only expose endpoints necessary for external access. 
• Validate all input data to prevent injection attacks and other vulnerabilities.
• Encode output data to prevent cross-site scripting attacks.
• Avoid exposing sensitive information during error handling. 
• Keep your API endpoints and underlying libraries up-to-date.

Keep APIs Updated

A part of the API security policy keeps your API software, libraries, and dependencies up to date. Follow these critical practices in this regard:

• Track all the third-party libraries and frameworks your API relies on. 
• Regularly review and update these dependencies. 
• Apply security patches once providers release software to address new potential vulnerabilities. 
• Automate these processes where possible. 

Log and Monitor Requests

Enable detailed logging of API requests and responses. This way, you will track software behavior and make it easier to detect the cause of any potential incident. 

Numerous real-time monitoring tools can detect unusual patterns or potential attacks. Also, set up alerts for critical security events, such as failed login attempts, unexpected API usage spikes, and unauthorized access attempts.

Conduct Regular Security Testing

There’s no need to run extensive security assessments for every sprint. Nevertheless, it’s best to initiate cybersecurity checks regularly. The list of such inspections includes the following: 

• Penetration testing to simulate real-world attacks and identify existing vulnerabilities

• Automated security scanning during development to detect issues early on
• Static application security testing to analyze your source code for weaknesses
• Dynamic application security testing to detect vulnerabilities in a live environment
• API fuzz testing to discover how it handles unusual requests
• Security testing integrated into the CI/CD pipeline

Know Your Vulnerabilities

It’s the foundation of a robust security strategy. Here’s how to discover potential vulnerabilities effectively:

• Identify potential threats, including those posed by third-party services or libraries.
• Analyze how those threats impact your systems. 
• Prioritize the threats that are most likely to occur. 
• Prepare a risk strategy to tackle each in case of an incident. 
• Be ready for a worst-case scenario and do everything to prevent it. 

Educate Your Team

Finally, encourage a security-first mindset in your organization. As beaten as it may sound, it’s one of the cornerstones of product security. In practice, everyone is responsible for contributing to the overall security posture. Explain this to your team and provide ongoing security training for developers and IT staff.

Conclusion

API cybersecurity design is a complex and ever-evolving subject. Technologies change rapidly, and so do cyber risks. Follow the practices above to set up secure connections between systems and reduce the risks associated with API usage. However, that’s not the most challenging part. API security design is not a one-time task but an ongoing process.

Regularly assess your security posture to ensure it remains effective, and stay updated on emerging threats. Continuously test your systems and adapt your strategy to the evolving tech landscape. Integrate security into the development lifecycle through DevSecOps practices, embedding automated security checks, continuous monitoring, and rapid vulnerability remediation throughout the development process. 

With a proactive approach to API security, you will safeguard your data, maintain customer trust, and ensure long-term software stability. For expert guidance on API security strategy, contact the Iterasec team to help you implement a tailored, comprehensive security solution.