In the modern digital landscape, APIs (Application Programming Interfaces) serve as the critical links that enable seamless communication between diverse software systems. While they empower innovation and functionality, APIs are also a prime target for cybercriminals seeking to exploit vulnerabilities.
API security testing ensures that your APIs are not just functional but secure against unauthorized access, data breach, and denial-of-service (DoS) attacks.
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8 API security testing steps
- Identify and categorize APIs
- Map out potential vulnerabilities
- Perform authentication and authorization tests
- Test input validation
- Analyze response handling
- Perform penetration tests
- Review rate limiting and throttling
- Conduct post-deployment security tests
Why do you need API security testing?
Without API security testing, businesses expose themselves to significant risks: malicious actors can exploit API weaknesses to access sensitive data or disrupt services. These breaches can lead to financial losses, reputational damages, and regulatory penalties. Moreover, as the use of APIs keeps on growing, the frequency of API attacks is also escalating, making security testing a must-have in your general cybersecurity strategy.
This can be achieved by integrating API security testing tools that will help identify API vulnerabilities early on, while risks are still low-cost to fix and before they become real-world issues. It also helps in ensuring API security standards compliance, including the OWASP API Top 10 vulnerabilities.
API security checklist
An API security checklist should be followed by a business in order for APIs to be continuously and reliably protected. Here is an extensive list to help guide your API security practices:
- Ensure that all API endpoints have strong authentication and authorization.
- Perform rate limiting and throttling to prevent abuses from too many requests.
- Validate all input fields against injection attacks.
- Encrypt sensitive data both in transit and at rest.
- Provide full logging and monitoring for all API activities.
- Regularly update and patch APIs to avoid exposing known vulnerabilities.
- Test APIs for compliance with the OWASP API Top 10.
- Employ API security testing tools to continuously scan for vulnerabilities.
This checklist will help you address the most critical aspects of API security and stay compliant with the set API security standards.
Common API vulnerabilities
Most of the time, APIs become an attack vector when there is an opportunity to take advantage of API vulnerabilities. Understanding and addressing common API vulnerabilities becomes an important activity in defending your systems against breaches, data theft, and other malicious activities.
The following are among the worst weaknesses affecting APIs, many of which are mentioned in the OWASP API Top 10.
Broken Object-Level Authorization (BOLA)
BOLA is a condition that occurs when an API does not properly enforce authorization at the object level. In other words, this is considered a BOLA vulnerability if an API does not check whether a given user has sufficient permissions to access certain data. Attackers can exploit BOLA by modifying the object identifier in an API request (such as a user ID or file reference) to access unauthorized data.
For example, in an e-commerce platform, the attacker may change the API requesting order details of another user by editing the order ID in the request URL. Without proper checks on authorization, such a vulnerability may cause huge data leakage, which can share sensitive information with unauthorized users.
How to prevent BOLA
- Implement robust authorization to check each API endpoint.
- Ensure that object identifiers are properly validated to match user permissions.
- Do regular API security testing to identify broken authorization problems.
Excessive data exposure
Excessive data exposure occurs when APIs return lots of data from the request returned by a client. Often, developers expose entire datasets and let the client-side application filter the information that it needs. However, such techniques have been exploited by merely intercepting the API response and getting sensitive data that was not intended for users.
For example, an API might send the entire customer record (including personal details like social security numbers or credit card information) to a mobile app, even though the app only displays the customer’s name and address. These types of exposures really heighten the risk of data breaches, especially if the sensitive data is unencrypted.
How to prevent excessive data exposure
- Limit returned data from APIs to only what is necessary to accomplish the required operation.
- Implement data filtering on the server side rather than relying on the client side.
- Encrypt data that is sensitive in transit as well as at rest.
Lack of rate limiting
APIs without rate limiting are prone to DoS attacks, where an attacker can easily send surplus amounts of API requests to the server. Without setting a limit on the number of requests within a certain given time, APIs can easily be exploited for poor performance, downtime, or even complete service and downtime.
The most prevalent form of this sort of attack is known as a brute force attack, whereby an attacker continually sends requests from a client attempting to guess login credentials or some sort of authentication token. Without proper limitations on the rate of requests, an attacker might easily reach hundreds or thousands of guesses per second, thus increasing the possibility for a breach.
How to prevent lack of rate limiting
- Implement rate limiting to restrict the number of API calls a client can make within a defined time period.
- Enforce throttling mechanisms to delay or block excessive requests.
- Leverage API security tools for monitoring traffic patterns that could indicate a potential DoS attack.
Poor logging and monitoring
Poor logging and monitoring of API activities in real time leaves an organization oblivious to the attacks and breaches that may be going on. In fact, poor logging and monitoring means malicious activities go unnoticed, thus allowing attackers to further exploit vulnerabilities without detection. Without proper logs, it is tough to trace the source that an attack emanated from or understand its impact.
For instance, if there is someone probing your API for weaknesses, it can log each and every request. Proper logging would make sure that your security team knows about the suspicious behavior so that remediation can be done well before the probe ever becomes a breach.
How to prevent poor logging and monitoring
- Implement comprehensive logging for all API requests and responses, including error handling.
- Utilize real-time monitoring to identify abnormal API traffic or other types of suspicious behavior.
- Logs should be kept in a secure way and checked regularly for signs of compromise.
Injection attacks
Injection attacks are one of the most well-known vulnerabilities and occur when untrusted data is sent to an API interpreter as part of a command or query. The most common types of injection attacks include SQL injection, XML injection, and command injection. These attacks allow an attacker to have the API do something it would not have otherwise done, or in ways they are not authorized to do, such as retrieve or modify sensitive information.
For example, in an SQL injection attack, an attacker can input malicious SQL statements into an API request that directly interacts with the database. If that API happens to fail or is unable to correctly sanitize user inputs, this would have a potential impact of an attacker retrieving data or making unauthorized changes to database records.
How to prevent injection attacks
- Sanitize and validate all user inputs before processing them into API requests.
- Interact with the database using solely either parameterized queries or stored procedures.
- Implement strong mechanisms for input validation and filtering on all API endpoints.
Poor asset management
Most of the time, APIs become increasingly difficult to oversee, especially for large organizations where different teams are in charge of different APIs. If proper management of assets is not done, it’s so easy to leave the APIs forgotten or unsecured, thus making them the first target of attackers.
This may lead to endpoints exposed, versions getting outdated, or APIs that contain sensitive information not currently monitored or maintained. For example, deprecating one version of an API but keeping it open without properly securing it might expose critical vulnerabilities.
How to prevent poor asset management
- Maintain an inventory of all the APIs, including but not limited to API versioning, API purpose, and applied security controls.
- Regularly audit and update API endpoints to ensure deprecation of out-of-date versions is removed or secured.
- Establish API lifecycle management processes that guarantee all APIs are monitored appropriately.
Mass assignment
Mass assignment vulnerabilities occur where an API endpoint automatically binds data from a request to model fields without filtering out sensitive or unintended fields. An attacker might leverage this to overwrite data they shouldn’t and modify key information in unauthorized ways.
For instance, an API request executed maliciously would update the attacker’s user profile to include administrative privileges using parameters, which, by design, the user should have no ability to update.
How to prevent mass assignment
- Use whitelisting, in which only the specific fields should be updated through API calls.
- Use strong validation and filtering of all API input parameters.
- Perform API security testing to find possible mass assignment vulnerabilities.
Security misconfigurations
Security misconfigurations can occur when an API is released to the environment while still in default or insecure settings, such as weak authentication methods, unnecessary HTTP methods (like PUT or DELETE), and default credentials. These misconfigurations may lead to unauthorized access, data disclosure, or other security breaches.
For example, it exposes the entire application to hackers when API keys or authentication tokens are left in publicly accessible locations, such as code repositories.
How to prevent security misconfigurations
- Regularly audit your API settings against cybersecurity best practices.
- Disable any unnecessary HTTP methods and features not being used.
- Use environment-specific configurations to avoid exposing sensitive settings in production environments.
Steps involved in performing API security testing
Performing API security testing is a must to secure your APIs; for that, you need a comprehensive, structured approach. The most important steps to be performed are highlighted below.
1. Identify and categorize APIs
Identify every API used in your application, be it internal, external, or third-party. Then, rank these according to purposes and sensitivity.
2. Map out potential vulnerabilities
Validate your APIs against a commonly known set of the most critical risks identified by OWASP API Top 10, including injection attacks, improper authentication, and data exposure.
3. Perform authentication and authorization tests
4. Test input validation
Validate all input that passes through an API. In many instances, this will prevent injection attacks.
5. Analyze response handling
Test your API’s response handling, especially for error responses. Poorly handled error responses may leak valuable information to an attacker.
6. Perform penetration tests
Real-world attacks can be simulated using API security testing tools. In addition, penetration testing assists in finding flaws normally not found by automated tools.
7. Review rate limiting and throttling
Make sure the APIs have rate-limiting mechanisms in place in order to protect them against DoS attacks.
8. Conduct post-deployment security tests
Regularly monitor APIs even after deployment for continuous identification and mitigation of new vulnerabilities through testing.
What to look for in API security testing vendors
Choosing the correct API security vendors is crucial for ensuring robust API protection. Several factors should be considered for evaluating vendors:
Comprehensive testing tools |
Look for vendors that deal with a wide set of API security testing tools and can offer multiple types of testing, such as SAST, DAST, and penetration testing. |
OWASP API standards compliance |
Ensure that the vendor’s tools and practices align with OWASP API Top 10 security risks and OWASP API security standards. |
Automation capabilities |
Vendors should provide automated security testing solutions integrated with your CI/CD pipeline to keep protection continuous. |
Real-time monitoring and alerts |
The solution vendor should be able to provide real-time threat monitoring that enables immediate threat containment. |
Customizable solutions |
Every business has different security requirements; hence, go for those vendors that provide flexible and customizable security testing solutions with your particular API needs. |
Reputation and support |
Consider the reputation of the solution provider in the market, support given to customers, and their experience in API security. |
Partner with the right security vendor
In today’s business environment, API security is essential, as APIs power the mission-critical functionality of modern apps. Whether you’re adhering to OWASP API Top 10 guidelines or leveraging the latest API security testing tools, comprehensive testing is key to protecting your business from breaches and ensuring a secure, reliable API ecosystem.
Partnering with the right security vendor is crucial to maintaining strong API defenses. Verimatrix, with its expertise in app security and cutting-edge tools, is the ideal partner to help shield your apps against ever-evolving threats and vulnerabilities. Check out our offers here.
