API is the abbreviation for application programming interface. Just like you would protect your basic information, like the password tied to your user identity on social media, it is equally important on the back end to protect API access, so that identifiers like API keys and API calls do not get misused.
It’s not surprising that APIs represent an increasing security risk, because any web application or web service available is almost certainly supported in some way by an API. From mobile applications and Internet of Things (IoT) devices to internal applications, cloud-based customer services, and microservices architectures, APIs make your business communication and transactions possible.
Consequently, web API security and API management must be a critical priority for your IT teams throughout the entire lifecycle of your APIs. But protecting APIs from security threats can be a complex challenge, thanks to cloud migration, modern DevOps practices, and constantly evolving APIs.
API Security: A Systematic Approach
API security is a systematic approach for protecting the APIs that organizations use to support their business processes. These may include:
- APIs that are implemented to make functionality and data easily accessible by customers or business partners
- APIs consumed by business partners
- APIs that are implemented and used internally, to make application functionality and data available to various systems and user interfaces in a standardized and scalable manner
An effective API security strategy must include systematic techniques for:
- Assessing risk and potential impact
- Executing appropriate mitigation measures
The first step in assessing risk is building an inventory of all sanctioned and unsanctioned APIs published and used by the organization. This inventory should include attributes such as:
- Data classifications, which at a minimum distinguish between “not sensitive,” “sensitive,” and “very sensitive” data
- Risk indicators, such as API vulnerabilities and misconfigurations
These are the essential building blocks for measuring impact and prioritizing mitigation efforts.
API visibility and risk mitigation measures must consider a diverse collection of possible threats, including:
- Detecting and preventing the use of unsanctioned “shadow APIs”
- Identifying and remediating API vulnerabilities and misconfigurations that malicious actors could potentially exploit
- Preventing instances of API misuse, like business logic abuse and data scraping
Identifying and mitigating these and other API security risks requires security controls that are sophisticated enough to address this complex and fast-evolving threat landscape. But equally important is finding ways to extend API security practices into non-security workflows that affect API security posture, such as software development and documentation.
Web APIs: The Basics
APIs, or application programming interfaces, are a key part of modern web development. But with great power comes great responsibility, and when it comes to APIs, that responsibility is security. API security is all about protecting the interfaces between applications. Without proper API security, sensitive data could be exposed, systems could be compromised, and services could be disrupted. Basically, API security is what keeps the bad guys out while letting the good guys do their work.
Authentication and Authorization
Two fundamental aspects of API security are authentication and authorization.
- Authentication is the process of verifying the identity of a user, device, or system. It’s like checking an ID at the door of a club — you need to make sure that the person trying to get in is who they claim they are.
- Authorization is about determining what a verified user can and can’t do. Just because someone is allowed in the club doesn’t mean they can go behind the bar and pour themselves a drink.
In the API world, authentication and authorization might involve techniques like API keys, tokens, or OAuth.
Input Validation: A Key to Web API Security
Another important aspect of API security is input validation. This involves checking that the data sent to an API is valid before it’s processed. Think of it like checking tickets at a movie theater — you wouldn’t let someone in with a ticket for a different movie, right? In the same way, input validation helps to prevent malicious data from getting into an API and causing trouble.
API Security 101
API security is one of the fastest-growing priorities for security executives. But it’s also arguably one of the least understood. The evolution of APIs from implementation detail to a strategic enabler of innovation has been a rapid one. As a result, many security teams are scrambling to increase the sophistication of their API security strategies and practices. APIs are enabling commerce, but they also carry sensitive data.
What is a Web API?
A web API is a programmatic interface consisting of one or more publicly exposed endpoints to a defined request–response message system, typically expressed in JSON or XML, which is exposed via the web — most commonly utilizing an HTTP-based web server.
When they hear “API,” what most people think of is a web API. It’s a collection of endpoints. Endpoints consist of resource paths, the operations that can be performed on these resources, and the definition of the resource data (in JSON, XML, protobuf, or another format).
The term is useful to differentiate web APIs from other APIs, such as those exposed by the operating system or by libraries to applications running on the same machine. But we all take “APIs” to mean HTTP-based (web) APIs when we talk about enterprise digital transformation and API security.
The Four Common Types of Web APIs
RESTful APIs
Representational state transfer is the most common type of web API, typically using JSON. They are easy to consume by modern front-end frameworks like React.
SOAP APIs
SOAP uses the verbose Extensible Markup Language (XML) for remote procedure calls (RPC). It can still be found in legacy APIs.
GraphQL APIs
Provides database access over a single POST endpoint. solves a common RESTful API problem — that of requiring multiple calls to populate a single UI page.
gRPC APIs
A new, Google-developed, high-performance binary protocol over HTTP/2.0, used mostly for east-west communication.
B2C vs. B2B APIs
Business-to-consumer (B2C) APIs power web and mobile applications. They are typically consumed by modern front-end clients to allow end users access to the company’s business functionality.
Business-to-business (B2B) APIs are used by the company’s business partners. Examples include Open Banking APIs, Supply Chain Management, and Electronic Invoicing. Protecting B2B APIs is a growing problem because dedicated visibility solutions are often lacking.
APIs vs. Endpoints
People often use the word “API” when what they are actually talking about is a single API endpoint. APIs (or services) are collections of endpoints that serve a business function. An endpoint is a resource path (URI) and the operation performed on it (GET, POST, etc.).
North-South vs. East-West APIs
- North-South APIs: Exposed to the outside world (partners, public). They are the fastest-growing attack surface.
- East-West APIs: Used internally to connect applications or departments.
Private vs. Public APIs
Private (internal) APIs are for company developers. Public (external) APIs are exposed to consumers outside. Note: Private APIs accessed over the internet (e.g., by a mobile app) are not truly private; they are simply undocumented public APIs, and hackers attack them daily.
How Big is the API Security Problem?
API security risks are already one of the most pressing risks faced by enterprise security teams. Usage is exploding due to microservices, modern front-end frameworks, and new channels (IoT/Partners). "By 2022, API abuses will move from an infrequent to the most-frequent attack vector, resulting in data breaches for enterprise web applications" (Gartner).
Web API Best Practices
We recommend organizations start with these 12 best practices:
- Integrate API security standards into the SDLC.
- Incorporate documentation and automated testing into CI/CD pipelines.
- Ensure appropriate authentication and authorization controls.
- Implement rate-limiting measures.
- Augment rate limiting with specialized gateways and CDNs to mitigate DDoS.
- Make API security testing part of broader application testing.
- Perform continuous discovery of APIs.
- Systematically identify and remediate vulnerabilities (OWASP API Top 10).
- Use signature-based threat detection as a baseline.
- Augment with AI and behavioral analytics for scalable detection.
- Ensure monitoring extends over multiple weeks and sessions.
- Complement monitoring with on-demand access to inventory for threat hunters.
Evaluating Your API Security Posture
The best way to approach API security best practices is by thinking in terms of organizational maturity, using the framework below.
CYBERSEC API Security Evaluation Framework
Access to Logs
Ensure comprehensive logging across all environments.
Discovery
Identify all microservices and external APIs.
Risk Audit
Audit for misconfigurations and sensitive data.
Detection
Use behavioral analytics to detect anomalies.
Response
Deploy automated, customizable playbooks.
Threat Hunt
Search historical data for hidden compromises.
Vulnerabilities and Attacks
What is an API vulnerability? A software bug or configuration error that an attacker can exploit. The OWASP API Top 10 is the standard list, covering authorization, authentication, and more.
How can APIs be abused?
- Vulnerability exploitation: Technical flaws like Log4j or Apache Struts.
- Business logic abuse: Exploiting implementation flaws to prompt unexpected behavior (e.g., bypassing payment steps).
- Unauthorized data access: BOLA, IDOR, BFLA.
- Account takeover (ATO): Using stolen credentials to hijack accounts.
- Data scraping: Aggressively querying public APIs to build datasets.
- Business Denial of Service (DoS): Exhausting resources with heavy queries (common in GraphQL).
Advanced Concepts
What is a Zombie API?
Deprecated endpoints that remain alive and accessible. They often lack modern security controls.
What are Shadow APIs?
APIs used by the organization but unknown to security teams. They can be found by analyzing logs from CDNs, Gateways, WAFs, and Kubernetes.
Behavioral Analytics
A security approach using machine learning to identify anomalies in user behavior. It is critical for API security to detect ATO, insider threats, injection attacks, and DoS.
Managed Threat Hunting
A proactive service where experts use advanced tools and historical data to hunt for potential threats before they cause damage.
Common API Misconfiguration Errors
- Broken or no authentication: Failing to protect sensitive data or ensure mechanisms resist brute-force attacks.
- Broken authorization: BOLA and BFLA vulnerabilities allowing access to other users' data.
- Security misconfiguration: Insecure communication (no TLS), unprotected cloud storage.
- Lack of resources and rate limiting: Allowing unlimited calls, leading to DoS.
API Security Solutions & Trends
An API security solution includes: Authentication/Authorization, API Gateways, Encryption, Rate Limiting, Auditing/Logging, API Testing, Monitoring/Runtime Protection, and Vulnerability Management.
Key Trends:
- Behavioral Analytics: Moving beyond signatures to detect context-aware anomalies.
- SaaS Delivery: Leveraging cloud scale for AI/ML analysis.
- Larger Time Windows: Analyzing activity over weeks/days, not just seconds.
- DevSecOps: Linking API security with development/CI/CD.
Based on industry standards and research from the Akamai Glossary.