API security is the practices, techniques, and technologies used to protect APIs from malicious attacks and unauthorized access. APIs are the building blocks of software development. They enable applications to communicate with each other, share data and extend functionalities. Attacking APIs provides attackers with access to sensitive data that flows between applications, servers and users. This makes APIs prime targets for cyber attacks, making their security top priority for organizations. Common security threats identified in the OWASP Top 10 for APIs include:

• Broken Authentication - Weaknesses in authentication mechanisms that allow attackers to assume the identity of legitimate users.
• Unrestricted Resource Consumption - DoS attacks or attacks that increase operational costs.
• Sensitive Data Exposure - Inadequate protection mechanisms that lead to unauthorized access to sensitive data.
• Security Misconfigurations - Configurations that are missed or don’t follow best practices, making them vulnerable to attacks.
• Unsafe Consumption - Targeted exploitation of third-party API services, since developers tend to trust them more.

API Security as Part of the Development Lifecycle

API security means safeguarding communication between the different software components and services, protecting business logic and sensitive data (like user details and payment information). This requires several strategic and technical measures throughout the development process:

• Design - Conceptualizing the necessary security measures. This includes incorporating authentication, authorization, data validation and rate limiting and building an API inventory.
• Development - Implementing security coding practices that can address the security risks associated with APIs, like in the OWASP API Security Top 10. This includes validating all data coming into and going out of the API, implementing proper authentication and authorization checks and encrypting sensitive data in transit and at rest.
• Testing - Incorporating API security testing as part of the API testing process. This includes conducting static and dynamic analysis to detect vulnerabilities, as well as penetration testing to identify weaknesses in authentication, authorization and business logic.
• Deployment and Maintenance - Continuous monitoring for vulnerabilities. This includes regularly reviewing access controls, auditing API usage for suspicious activity and updating APIs to patch known vulnerabilities.

Why is API Security Important?

APIs serve as the conduits through which different software applications and services communicate and exchange data. Most cloud-based applications, like mobile apps and SaaS applications, rely on them. As such, they often handle sensitive data, including personal information, financial details, proprietary business information and application logic. In addition, APIs can serve as gateways to underlying systems and services. Securing APIs ensures that data is transmitted safely and only accessible to authorized parties. This prevents malicious actors from exploiting vulnerabilities that could enable them to manipulate system behavior, inject malicious code, or disrupt service availability. These activities could impact both the enterprise and its partners, vendors and customers.

How Does API Security Work?

API security protects from data breaches, loss of customer trust, regulatory penalties and financial loss. Mitigating these risks requires a comprehensive approach to API security, including:

• Implementing strong authentication and authorization mechanisms.
• Ensuring sensitive data is encrypted in transit and at rest.
• Implementing rate limiting and throttling mechanisms to limit user requests and prevent DoS attacks. 
• Adopting input validation techniques to prevent injection attacks.
• Employing API gateways for rate limiting, access control and traffic management.
• Implementing security policies with guidelines for secure coding practices, updates, patches and IR plans.
• Rigorous security testing, including penetration testing and vulnerability scanning, to identify and address weaknesses.
• Adhering to security standards and protocols
• Continuous monitoring and logging of API activities to detect and respond to threats promptly.

• Training the development, operations and security teams so they are educated about the latest API security threats and best practices.

Benefits of API Security

Securing APIs is a key practice in the enterprise security plan. This is because it ensures:

• Operational Continuity - Security incidents can lead to significant disruptions in business operations. By securing APIs against attacks, organizations can ensure continuity, minimize downtime and maintain operational efficiency.
• Meeting Regulatory Compliance - Many industries are governed by stringent regulatory standards that mandate the protection of customer data (e.g., GDPR, HIPAA, PCI DSS). Implementing comprehensive API security helps organizations comply with these regulations and avoid potential fines and legal repercussions.
• Enhanced Security Posture - API security measures strengthen the overall security posture of an organization by protecting backend systems from various attack vectors.
• Trust and Reputation - By demonstrating a commitment to API security, organizations can build and maintain trust with their customers.
• Innovation and Speed to Market - Secure APIs facilitate safe and rapid integration of new features and services, allowing organizations to accelerate development cycles and bring new products to market more quickly.
• Cost Savings - Addressing security issues post-deployment can be costly and resource-intensive. By integrating security into the API development lifecycle, organizations can identify and mitigate vulnerabilities early, reducing the costs associated with remediation efforts, data breaches and non-compliance penalties.
• Scalability and Flexibility - Secure APIs are designed to handle increased loads and adapt to changing business needs without compromising security. This scalability and flexibility support business growth and enable organizations to quickly adapt to market demands or technological advancements.
• Competitive Advantage - Organizations that prioritize API security can differentiate themselves from competitors. This can be a decisive factor for customers and partners when choosing between services, particularly in industries where data security is a top priority.
• Increased Profitability - Security breaches can have significant economic repercussions, from immediate financial losses due to fraud or theft to longer-term costs associated with remediation, legal fees and increased insurance premiums.

API Security Concerns

When security leaders implement API security tools in their stack, they are protecting organizations from business operations disruptions. This includes protecting against:

• Excessive data exposure by developers who might inadvertently include sensitive information in API responses
• Unauthorized access to sensitive functions and data
• Injection attacks, such as SQL injection, Command injection, and more
• Vulnerabilities in API Gateways and proxies
• Rate limiting and DDoS attacks that make APIs unavailable to legitimate users
• Inadequate encryption of data being transmitted over APIs
• API Key mismanagement due to exposing API keys in client-side code or not rotating them
• Inadequate monitoring and logging of API activities
• Vulnerable third-party APIs and service integrations
• And more

API Security Best Practices

Here are some actionable best practices for enhancing API security that AppSec teams can share with developers:

1. Use HTTPS to encrypt data transmitted between the client and the API server. This prevents man-in-the-middle attacks and ensures that sensitive information, such as authentication tokens and personal data, is securely transmitted.
2. Implement strong authentication and authorization mechanisms like OAuth, API keys and JWT for authentication and RBAC or ABAC for authorization. This controls access to your APIs.
3. Validate and sanitize all input data to prevent common vulnerabilities such as SQL injection, cross-site scripting (XSS) and command injection attacks.
4. Implement rate limiting to control the number of requests a user can make to an API within a certain timeframe. This practice helps mitigate DoS attacks and ensures that APIs remain available to all users by preventing any single user or service from overwhelming the API with excessive requests.
5. Use API gateways to enforce SSL/TLS termination, authentication, rate limiting and IP whitelisting.
6. Ensure that all API endpoints are secure against unauthorized access. This includes securing less obvious or undocumented APIs that might be overlooked but could provide attackers with a backdoor if left unprotected.
7. Continuously monitor API usage and log activities to detect and respond to suspicious behavior or potential security incidents. Effective monitoring and logging can aid in identifying attack patterns, troubleshooting issues and providing forensic data in the event of an attack.
8. Regularly update and patch APIs and their dependencies to protect against known vulnerabilities. Subscribe to security bulletins and use automated tools to stay informed about new vulnerabilities and patches for your APIs and related software
9. Encrypt sensitive data stored by the API to protect it from unauthorized access or in the event of a data breach. Use strong encryption standards and manage encryption keys securely.
10. Implement security headers to protect your API from common attacks. This includes headers like CSP to prevent XSS attacks, X-Content-Type-Options to stop MIME-sniffing and HSTS to enforce secure connections.
11. Choose a comprehensive API security solution that helps detect API vulnerabilities early on, like Checkmarx One.

API Security and Checkmarx

Checkmarx helps organizations discover all APIs in code so security issues can be addressed early in the SDLC. Checkmarx One provides API Security, listing the entire API inventory, exposing Shadow APIs and Zombie APIs and identifies existing vulnerabilities and risks related to them with one single application on a unified platform from code-to-cloud. AppSec teams no longer need multiple API-specific tools. Capabilities include:

• Automatic API discovery - Identifying API endpoints without requiring manual API definition or registration by AppSec teams or developers.
• Complete API inventory - Discovering newly created or updated APIs as developers check in or compile the source code as early as possible in the software development cycle.
• Unknown API identification - Comparing the full API inventory of an application with its API documentation to identify unknown, Shadow and Zombie APIs.
• Prioritized remediation - Helping developers and AppSec teams to solve the most critical issues by prioritizing API vulnerabilities based on their real impact and risks.
• Whole application coverage - Providing a single AST solution for the entire application, which may have API- and non-API-based components, for a holistic view of security risk and prioritization for vulnerability remediation.
• True shift-left approach - Discovering APIs in application source code to identify and fix problems early in the software development cycle.

Learn more about Checkmarx API Security here.