Watch this Radware Minute episode with Radware’s Uri Dorot to learn what APIs (Application Programming Interfaces) are, what cyber threats they are exposed to, why it is so important to protect your organization’s APIs and what to look for when evaluating API protection solutions
What Is API Security?
Application programming interface (API) security involves strategies and solutions for mitigating API security vulnerabilities and cyberattacks targeting APIs. The purpose of API security is to detect, mitigate and prevent malicious attacks by hackers seeking to penetrate the network and compromise APIs. Application security should provide full coverage of the OWASP API Security Top 10 attacks, including protecting from all forms of injections, XSS, access violations and DoS/DDoS.
An API is an interface that defines how different software programs interact. It controls the types of requests that occur between programs, how these requests are made, and the kinds of data formats that are used. APIs are used in web applications, cloud computing, enterprise software, the Internet of Things (IoT), and almost everywhere modern software products are deployed. They often gather and process data, or allow the user to input information that gets processed within the environment housing the API.
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Businesses use APIs to connect services and to transfer data. Major data breaches occur due to broken, exposed or hacked APIs which can expose sensitive medical, financial, and personal data for public consumption. However, not all data is the same, nor requires to be protected in the same way. How you approach API security depends on the kind of data that is being transferred.
API security focuses specifically on protecting the communication pathways between software components, while general application security encompasses a broader set of practices aimed at safeguarding the entire application. The key differences include:
- Focus on communication layers: General application security often targets threats to the application as a whole, including user interfaces, backend systems, and databases. In contrast, API security emphasizes protecting the exchange of data between systems, ensuring that these interactions remain secure, authenticated, and authorized.
- Unique vulnerabilities: APIs are particularly vulnerable to issues like broken object-level authorization, insufficient logging and monitoring, and mass assignment attacks. These issues are less prevalent in traditional application security, which often focuses on threats like SQL injection or cross-site scripting (XSS) in the user interface layer.
- Dynamic exposure: APIs frequently expose endpoints that grant access to core application functionalities. These endpoints, if improperly secured, provide a direct pathway to sensitive data or operations. General application security does not always involve such granular access control.
- Authentication and authorization: API security places a heavy emphasis on robust authentication (e.g., OAuth, API keys) and fine-grained authorization mechanisms for each endpoint. General application security often employs broader, session-based approaches to manage user access.
- Machine-to-machine interactions: Unlike general application security, which is typically concerned with protecting interactions between humans and applications, API security must secure interactions between applications, often without direct human oversight. This introduces challenges in areas like credential management and securing automated processes.
There are important differences in the security practices for different API architectures: REST, SOAP, and the newer GraphQL.
REST API Security
REST APIs are widely used due to their simplicity and scalability. They leverage HTTP methods like GET, POST, PUT, and DELETE, making them stateless and lightweight. Key security considerations include:
- Authentication and authorization: Implement token-based authentication methods, such as OAuth 2.0 or JSON Web Tokens (JWT). REST APIs often use HTTPS to encrypt data in transit.
- Input validation: Validate all inputs to prevent injection attacks. REST endpoints are often vulnerable to improper input handling.
- Rate limiting and throttling: Use rate-limiting strategies to mitigate DoS/DDoS attacks by controlling the number of requests per user or IP.
- Secure data handling: Avoid exposing sensitive information in URLs, as they are logged in browsers and servers. Use request headers or body for sensitive data transmission.
SOAP Security
SOAP APIs are based on an older standard, which is still widely used, and is designed for more structured and secure communication. They rely on XML-based messaging and adhere to strict protocols, often making them preferred in enterprise environments. Key security considerations include:
- WS-Security standards: SOAP supports WS-Security for message-level security, enabling features like XML encryption, signing, and token-based authentication.
- Transport Layer Security (TLS): SOAP APIs commonly use TLS to ensure secure communication.
- Complexity and granularity: The strict schema of SOAP provides detailed error handling but can expose vulnerabilities if the schema is improperly configured.
- Access control: Strong authentication and authorization mechanisms are essential, as SOAP APIs often integrate with critical business systems.
GraphQL Security
GraphQL provides a flexible query language, allowing clients to request specific data. However, its flexibility introduces unique security challenges. Key considerations include:
- Query complexity limiting: Monitor and restrict query depth and breadth to prevent resource exhaustion attacks, such as DoS through overly complex or nested queries.
- Authentication and authorization: Implement robust user authentication and field-level authorization to ensure only permitted data is accessible.
- Validation and sanitization: Validate all incoming queries to avoid injection attacks. Since GraphQL relies on dynamic query construction, improper handling can lead to vulnerabilities.
- Introspection restrictions: Disable introspection queries in production environments to limit attackers' visibility into the API structure.
Security for Common API Architectures: Summary Table
| Aspect |
REST API |
SOAP API |
GraphQL |
| Ease of Use |
Simple, lightweight |
Strict, enterprise-grade |
Flexible, dynamic |
| Security Standards |
OAuth, JWT, HTTPS |
WS-Security, TLS |
Custom mechanisms, query limiting |
| Primary Concerns |
Endpoint security, input validation |
Schema security, message integrity |
Query complexity, introspection |
| Best Use Cases |
Web and mobile applications |
Financial or enterprise systems |
Data-driven apps needing flexibility |
The OWASP API Top 10 is a list of the most critical security risks for APIs, providing a roadmap for developers and security professionals to identify and mitigate vulnerabilities. Below are the threats, in order of severity, and their implications:
- Broken Object-Level Authorization (BOLA): This occurs when an API fails to enforce access controls properly, allowing attackers to manipulate object identifiers to access unauthorized data. It can lead to data leaks or unauthorized actions.
- Broken User Authentication: APIs that lack robust authentication mechanisms are vulnerable to impersonation attacks. Weak password policies, lack of multifactor authentication, or improper session handling can allow attackers to compromise user accounts.
- Excessive Data Exposure: APIs often return more data than necessary, relying on clients to filter the response. This can unintentionally expose sensitive information to attackers.
- Lack of Resources and Rate Limiting: APIs without rate-limiting controls can be exploited to execute brute-force attacks or overload the system with requests, leading to Denial of Service (DoS) or degraded performance.
- Broken Function-Level Authorization (BFLA): Insufficient authorization checks at the function level can allow attackers to execute administrative or privileged operations they should not have access to.
- Mass Assignment: This occurs when an API blindly binds user-provided data to model objects without validating the inputs. Attackers can exploit this to modify sensitive or unintended fields.
- Security Misconfiguration: Poorly configured APIs—such as default credentials, open endpoints, or missing security headers—can be easily exploited by attackers to gain unauthorized access or launch other attacks.
- Injection Attacks: APIs vulnerable to injection attacks, such as SQL, NoSQL, or command injection, allow attackers to execute malicious code or queries, leading to data compromise or system breaches.
- Improper Asset Management: APIs often have multiple versions or exposed endpoints. Failing to deprecate older versions or maintain proper documentation can leave legacy vulnerabilities open to exploitation.
- Insufficient Logging and Monitoring: Without adequate logging and monitoring, suspicious activities may go undetected. This can delay response to an attack and increase the impact of a breach.
In addition to the OWASP top 10 attack vectors, here are a few common methods attackers use automated systems, primarily bots, to attack API systems.
API Abuse
Attackers reverse engineer mobile and web applications to hijack API calls, and program bots to invade the business APIs. They target APIs to take over accounts, scrape business-critical data and perform application distributed denial of service (DDoS) attacks. Bots deluge the API server with unwanted requests. It is essential to distinguish accurately between good API calls and bad API calls, for online businesses.
Vulnerabilities in APIs are abused by cybercriminals and nefarious parties to steal Personally Identifiable Information (PII) and business-critical data, carry out account takeover attacks and systematically execute website content scraping campaigns. The types of bot-executed API abuse attacks include application DDoS, account takeover and web scraping.
Application DDoS
APIs can be attacked by hackers and cybercriminals who intentionally overload APIs with large volumes of bot traffic from multiple devices and IP addresses. For enterprises, business-critical services are thus put at risk, such as login services, session management and other services that enable application uptime and availability for users.
Attackers who carry out DDoS campaigns often use asymmetrical techniques through which they send small volumes of data to generate API calls, which usually result in servers being heavily overloaded as they need to answer such API calls with much larger volumes of data. These attacks seriously tie up system resources, and greatly increase the server response times for all users of the system.
Credential Stuffing
Credential stuffing exploits users’ propensity to use the same username and password on multiple websites. Hackers use bots to test lists of credentials obtained as a result of data dumps of breached credentials (or purchased from the dark web), against a range of websites in the hope that a victim has used the same combination of credentials on multiple sites. Unlike credential cracking, credential stuffing does not involve brute force or guessing of any values; instead, mass login attempts are used to verify the stolen username and password pairs. Credential stuffing symptoms include consecutive login attempts with different credentials from the same HTTP client.
Credential Cracking or Brute Force
Also known as “brute forcing,” credential cracking is a way to identify valid credentials by trying different values for usernames and passwords (usually from lists of breached account credentials that were made public by malicious parties and hackers). Hackers deploy bots to hack into customers’ accounts using the brute force approach, dictionary attacks (inputting large numbers of words) and guessing attacks to identify valid login credentials. Brute force attack symptoms include a sudden increase in failed login attempts and high numbers of account hijacking complaints from customers.
Account Takeover
Account takeover (ATO) is a form of identity theft where a fraudster illegally uses bots to get access to a victim’s bank, e-commerce site or other types of accounts. A successful ATO attack leads to fraudulent transactions and unauthorized shopping from the victim’s compromised account. Fraudsters use two primary methods to hijack accounts: credential stuffing and credential cracking.
Web Scraping
Competitors, fraudsters, and fly-by-night operators who set up websites to defraud consumers often plagiarize an entire website’s content by carrying out systematic scraping campaigns, using bots to extract data from APIs. Hackers also try to reverse engineer web and mobile applications to hijack API calls and carry out scraping attacks.
1. Enforce Strong Authentication and Authorization
Authentication ensures the identity of users or systems accessing the API, while authorization defines what actions they are permitted to perform. To secure APIs effectively, use robust mechanisms like OAuth 2.0 or OpenID Connect, which support secure token-based authentication and minimize the risks of credentials being compromised during transmission. For applications requiring heightened security, implement multifactor authentication (MFA), requiring users to validate their identity through multiple methods, such as passwords combined with biometrics or one-time passcodes.
Authorization should enforce granular access controls, applying role-based access control (RBAC) or attribute-based access control (ABAC). For example, a user with "read-only" permissions should not be able to perform write or delete actions. Additionally, segregate system-level and user-level access, ensuring API keys for backend services have distinct privileges separate from end-user tokens. By combining these measures, you reduce the likelihood of unauthorized actions being performed on your APIs.
2. Validate and Sanitize Inputs
Input validation is one of the most critical steps to ensure APIs do not process malicious or malformed data. For example, user-provided inputs, such as query parameters, headers, and request bodies, must be checked against strict rules. Ensure inputs conform to expected data types, lengths, formats, or allowed ranges. For example, if an API expects a numeric ID, reject any input containing non-numeric characters.
Sanitization further removes malicious content, especially in APIs that handle user-generated inputs. Escaping or encoding dangerous characters can prevent injection attacks, such as SQL injection or cross-site scripting (XSS). For APIs interacting with databases, always use parameterized queries to avoid direct embedding of user inputs into SQL statements. Validation libraries and frameworks can simplify enforcing these practices, ensuring consistency and reducing developer errors.
3. Implement Rate Limiting and Throttling
Rate limiting and throttling protect APIs from abuse by restricting the number of requests a client can make within a specified timeframe. This can prevent Denial of Service (DoS) attacks, where attackers flood the API with excessive requests, causing service degradation or downtime.
For example, set limits such as “100 requests per minute per user” and enforce them through API gateways or load balancers. Use algorithms like the token bucket or leaky bucket, which allow a steady request flow while permitting occasional bursts within defined limits. For more sensitive endpoints, such as those handling financial transactions, enforce stricter rate limits to prevent brute force or abuse attempts. Throttling can also help balance traffic loads, prioritizing genuine users while blocking malicious or high-frequency requests.
4. Secure API Endpoints
API endpoints are the primary points of interaction and are highly targeted by attackers. Start by encrypting all communications using HTTPS, which ensures that data exchanged between clients and servers cannot be intercepted or altered by attackers. Secure APIs by avoiding information leakage; for example, do not expose stack traces, server configurations, or other debug details in API responses.
Endpoints should also implement measures like IP whitelisting, where only specific IP addresses or ranges are permitted to access critical services. Utilize content security policies (CSPs) to prevent injection-based attacks. Furthermore, implement mechanisms to validate user sessions and tokens, ensuring requests come from legitimate sources. The use of strong TLS configurations and periodic certificate updates further fortifies endpoint security.
5. Monitor and Log Activity
Monitoring and logging provide visibility into API usage and help detect anomalous behavior. Log details such as request origins, user identities, timestamps, and resource access patterns. Centralize logging data in a system compatible with Security Information and Event Management (SIEM) tools, enabling real-time analysis and alerting.
For example, suspicious activity such as repeated failed login attempts or unusually high traffic from a single IP address could indicate brute force attacks or DDoS attempts. Integrate monitoring solutions like Prometheus, ELK Stack, or Datadog to visualize API performance metrics, detect anomalies, and trigger automated responses to mitigate potential threats.
6. Control API Exposure
The principle of least privilege should govern API exposure. Only expose endpoints that are essential for the API’s functionality and restrict access to sensitive resources. Employ API gateways to enforce policies like geofencing, IP blacklisting, or rate limiting at the network level. For APIs that handle sensitive operations, implement additional security measures, such as requiring elevated permissions or re-authentication for access.
Deprecate older API versions that no longer meet security standards. For instance, an API version relying on outdated encryption protocols should be retired promptly to avoid exploitation. Maintain clear documentation about API endpoints and their intended use cases to help developers avoid accidental misuse or exposure of critical functions.
7. Perform Security Testing and Reviews
Security testing ensures that vulnerabilities are identified and remediated before APIs are deployed to production. Use tools like Burp Suite, OWASP ZAP, and Postman to perform static application security testing (SAST) and dynamic application security testing (DAST). Fuzz testing, which involves sending random or invalid data to APIs, can help identify unexpected behaviors or crashes that attackers could exploit.
Regularly schedule penetration tests to simulate real-world attacks and uncover hidden vulnerabilities. Pair automated tests with manual code reviews for critical areas, ensuring security measures are correctly implemented. Maintain an incident response plan to address vulnerabilities quickly if discovered in live APIs.
8. Protect Against Bots and Automated Attacks
APIs are frequent targets of bots and Distributed Denial of Service (DDoS) attacks, which can disrupt services, degrade performance, and compromise data. Anti-DDoS solutions mitigate these threats by filtering malicious traffic and enforcing rate-limiting policies that cap the number of requests from a single source. Cloud-based services can absorb and distribute massive attack traffic across global networks, ensuring uptime during high-traffic events. Layered defense mechanisms address threats at the network and application layers, blocking volumetric floods like SYN floods and application-layer attacks like Slowloris.
Bot management solutions differentiate legitimate users from automated threats through behavioral analysis, CAPTCHA challenges, and device fingerprinting. Advanced tools detect patterns typical of bots, such as repetitive or high-speed requests, and use IP reputation databases to block known attackers. Honeypots and decoys attract malicious bots, enabling their isolation without affecting genuine traffic. Combining anti-DDoS services with bot detection and mitigation strategies ensures a comprehensive defense, maintaining API performance and availability while reducing the impact of malicious automation.
Radware offers industry-leading, analyst-recommended solutions for comprehensive API security, including:
Alteon Integrated WAF
Radware’s Alteon Integrated WAF ensures fast, reliable and secure delivery of mission-critical Web applications and APIs for corporate networks and in the cloud. Recommended by the NSS, certified by ICSA Labs, and PCI compliant, this WAF solution combines positive and negative security models to provide complete protection against web application attacks, access violations, attacks disguised behind CDNs, API manipulations, advanced HTTP attacks (such as slowloris and dynamic floods), brute force attacks on login pages, and more.
API Protection
Radware’s API Protection solution is designed to safeguard APIs from a wide range of cyber threats, including data theft, data manipulation, and account takeover attacks. This AI-driven solution automatically discovers all API endpoints, including rogue and shadow APIs, and learns their structure and business logic. It then generates tailored security policies to provide real-time detection and mitigation of API attacks. Key benefits include comprehensive coverage against OWASP API Top 10 risks, real-time embedded threat defense, and lower false positives, ensuring accurate protection without disrupting legitimate operations.
Bot Manager
Radware Bot Manager is a multiple award-winning bot management solution designed to protect web applications, mobile apps, and APIs from the latest AI-powered automated threats. Utilizing advanced techniques such as Radware’s patented Intent-based Deep Behavior Analysis (IDBA), semi-supervised machine learning, device fingerprinting, collective bot intelligence, and user behavior modeling, it ensures precise bot detection with minimal false positives. Bot Manager provides AI-based real-time detection and protection against threats such as ATO (account takeover), DDoS, ad and payment fraud, and web scraping. With a range of mitigation options (like Crypto Challenge), Bot Manager ensures seamless website browsing for legitimate users without relying on CAPTCHAs while effectively thwarting bot attacks. Radware Bot Manager delivers real-time insights into bot traffic, helping organizations safeguard sensitive data, maintain user trust, and prevent financial fraud.
Cloud WAF
Radware’s Cloud WAF service is part of our Cloud Application Protection Service which includes WAF, API protection, Bot management, Layer-7 DDoS protection and Client-Side Protection. The service analyzes web apps to identify potential threats, then automatically generates granular protection rules to mitigate those threats. It also offers device fingerprinting to help identify bot attacks, AI-powered API discovery and protection to prevent API abuse, full coverage of OWASP Top 10 vulnerabilities, and data leak prevention, which prevents the transmission of sensitive data. Radware Cloud WAF is NSS recommended, ICSE Labs certified, and PCI-DSS compliant.
See Additional Guides on Key Cybersecurity Topics
Together with our content partners, we have authored in-depth guides on several other topics that can also be useful as you explore the world of cybersecurity.
OWASP
Authored by Radware