What is an API attack, and how to prevent it?

Explore common API attacks, understand their significant risks, and learn how to prevent them.

What is an API attack, and how to prevent it?

The explosive growth of APIs throughout the last years has resulted in an increasing number of potential vulnerabilities. Hackers continue to exploit them, most of the time not ethically. This trend is especially alarming to sensitive domains like healthcare, banking, or government but is also quickly affecting other areas. Making sure APIs stay secure would require not only a lot of technical efforts but organizational ones as well.

But before securing APIs, we need to understand how they can be attacked and what qualifies as an API attack. In this article, we'll explore what an API attack is, understand the significant risks each attack represents, and, of course, learn how to prevent them.

What's an API attack?

An API attack is a set of actions dedicated to intentionally exploiting or misusing an API, typically with the goal of compromising data security or disrupting a business.

In 2023 the Open Web Application Security Project (OWASP) updated its API Security Top 10 list of vulnerabilities. In our article, we'll cover the most common ones among them:

Injection Attacks: Attackers input malicious data into the API hoping to induce unintended behavior. For instance, in SQL injection, malicious SQL code gets introduced into input fields, potentially exposing, altering, or deleting database contents.

Cross-Site Request Forgery (CSRF): An attack that forces users to perform unwanted actions on a web application where they are currently authenticated.

Broken Authentication: APIs might not always thoroughly verify a user's identity. This oversight means that if credentials are guessed, leaked, or mishandled, unauthorized individuals could gain system access, leading to potential data breaches or misuse.

IDOR (Insecure Direct Object References): This vulnerability arises when an attacker accesses objects, such as database entries, directly by manipulating input values. Without proper authorization checks, confidential data or system functionalities could be exposed.

Are you curious about real-life examples of IDOR? Learn more here.

Excessive Data Exposure: Sometimes, APIs disclose more information than they should, either in responses or error messages. This oversharing can provide attackers with valuable insights or data, which could be exploited further in targeted attacks.

Denial of Service (DoS): Attackers flood the API with an overwhelming volume of requests, aiming to exhaust its resources. This bombardment can slow down service or make it entirely unavailable for genuine users, disrupting normal operations.

API Fingerprinting: Through careful observation and analysis of an API's responses, errors, and patterns, attackers can infer its underlying technology, structure, and potential weak points. This information can then be used to craft more sophisticated attacks.

Rate Limiting Bypass: To protect against overuse or abuse, APIs often set a cap on request frequency. However, attackers might find ways to sidestep these limits, either to gain faster access or to instigate a DoS attack.

Now that we've explored the various types of API attacks, it's essential to understand why it's crucial to prevent them.

Why is it important to prevent API attacks?

The consequences of these attacks can be severe, as we'll delve into below, highlighting the importance of stopping API attacks per each attack type.

Injection Attacks: Successful injection attacks can lead to unauthorized access to sensitive data, data corruption, or even data loss. In the context of SQL injection, for example, attackers might retrieve confidential information, modify database content, or delete entire tables, causing data breaches and system malfunctions.

Cross-Site Request Forgery (CSRF): An attacker can perform actions on behalf of an authenticated user without their knowledge. These actions can range from changing email addresses, passwords, making unauthorized transactions, and more, depending on what the application permits the authenticated user to do.

Broken Authentication: If attackers exploit authentication weaknesses, they can impersonate legitimate users, gaining unauthorized access to protected areas or data. This can lead to data breaches, unauthorized data manipulation, or the execution of malicious actions under the guise of a valid user.

IDOR (Insecure Direct Object References): By exploiting IDOR vulnerabilities, attackers can bypass authorization and access sensitive data or resources. This might expose confidential user information or allow unauthorized modifications, leading to data integrity issues and potential breaches.


Excessive Data Exposure: When APIs reveal too much, attackers can gather valuable data for more targeted subsequent attacks. Overexposure can also lead to direct data breaches if personal or sensitive information is disclosed, damaging user trust and possibly leading to legal repercussions.

Denial of Service (DoS): A successful DoS attack can render the targeted API, or even the entire system, unavailable. This disruption can halt operations, frustrate genuine users, lead to financial losses, and damage an organization's reputation.

If you're working with GraphQL APIs, learn here how to avoid Denial of Service attacks through batching and aliasing

API Fingerprinting: Once attackers gain detailed insights into an API's structure and technology, they can craft more precise attacks, exploiting known vulnerabilities of the identified technology stack. This increases the likelihood of a successful breach or system compromise.

Rate Limiting Bypass: Circumventing rate limits can lead to system strain or contribute to DoS attacks. Additionally, rapid, unchecked access might allow attackers to probe the system more quickly for vulnerabilities or to extract data at an accelerated pace.

To mitigate the risks associated with API attacks, it's essential to implement effective security measures. Let's explore some solutions for each type of API attack we discussed earlier.

How to prevent API attacks?

Imagine one day you wake up and find out all your company's data was stolen, but you know you could have stopped it? Wouldn't you regret that you haven't implemented those protections in place? Now it's time to dive into practical steps to stop API attacks and enhance overall API security.

Injection Attacks: Always validate, sanitize, and/or escape user inputs. Employ prepared statements for database queries to prevent SQL injection. Use parameterized queries and ORM (Object-Relational Mapping) systems to further insulate your API from injection risks.

Cross-Site Request Forgery (CSRF): Allow only POST requests to perform data-altering actions and implement other measures as well like Challenge-Response, Synchronizer Token Pattern / CSRF token and more.

Broken Authentication: Implement strong authentication mechanisms, such as OAuth 2.0. Implement authorization properly by defining an access control policy.

IDOR (Insecure Direct Object References): Ensure proper authorization checks for every request. By implementing robust access control checks, validating user inputs, enforcing object-level authorizations, and using UUIDs, you can mitigate the risks associated with IDOR in GraphQL.

Excessive Data Exposure: Adhere to the principle of least privilege, ensuring that only necessary data is exposed. Trim API responses to only include essential data. Always mask or encrypt sensitive data and avoid revealing detailed error messages.

Denial of Service (DoS): Employ rate limiting to restrict the number of requests from a single source in a given timeframe. Use caching mechanisms to reduce server load. Avoid GraphQL Denial of Service attacks through batching and aliasing.

API Fingerprinting: Limit the information disclosed in headers, status messages, and error responses. Keep software updated to ensure known vulnerabilities are patched. Regularly monitor and analyze API traffic for suspicious patterns.

Rate Limiting Bypass: : Implement robust rate limiting mechanisms that use a combination of IP, token, and user-based restrictions. Ensure that rate limits are enforced server-side and are not reliant solely on client-side controls. Regularly monitor traffic for abnormal patterns indicating potential bypass attempts.

Securing APIs requires a combination of best practices, rigorous testing, and ongoing monitoring. Want to get risk monitoring in real time? Try Escape to automate your API security throughout your pipeline.

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