API Attacks: 10 Common Attacks and How to Prevent Them

APIs are a frequent target for attackers exploiting various vulnerabilities. Here’s a breakdown of the most common types of API attacks:

1. Injection Attacks

Injection attacks occur when attackers send malicious data to an API, allowing them to manipulate queries or execute harmful commands.

A typical example is SQL injection, where attackers insert malicious SQL code into API parameters. For instance, if an API accepts a user ID without validation, an attacker might send '; DROP TABLE users; -- instead of a valid ID, potentially deleting critical database tables.

Similarly, NoSQL injection targets databases like MongoDB by manipulating JSON parameters to bypass authentication or extract data. Another form, OS command injection, involves executing system commands via endpoints that fail to sanitize inputs.

2. Broken Authentication

Broken authentication happens when attackers exploit weaknesses in how APIs handle user credentials or tokens. Vulnerabilities include weak password policies, poor session management, and insecure token handling. For example, APIs that fail to validate JSON Web Tokens (JWTs) properly may allow attackers to forge credentials. Additionally, long-lived tokens without proper expiration policies are prone to theft.

Credential stuffing is another issue, where attackers use stolen username-password pairs from data breaches to access accounts. APIs lacking protections against brute-force attacks are especially vulnerable.

3. Broken Object Level Authorization (BOLA/IDOR)

Also known as Insecure Direct Object References (IDOR), this vulnerability arises when APIs expose endpoints that handle object identifiers without strict access controls. Attackers can manipulate these identifiers to access unauthorized data. For example, changing a URL parameter from /api/users/123/profile to /api/users/124/profile might expose another user's profile. This issue is particularly risky in mobile and single-page applications where object identifiers are often visible.

4. Excessive Data Exposure

Excessive data exposure occurs when APIs return more information than necessary, unintentionally revealing sensitive details. This often results from developers returning entire database objects instead of just the required fields. For example, a user profile API might inadvertently expose data like social security numbers or password hashes alongside public information.

The problem is amplified when APIs are designed to serve multiple applications with varying data needs, increasing the chance of unintentional disclosures.

5. Security Misconfiguration

Security misconfiguration stems from improper settings or default configurations in APIs and their systems. Examples include exposed debug interfaces, unauthenticated endpoints, weak HTTP headers, or default credentials. For instance, leaving debug modes enabled in production can leak sensitive system details. Misconfigured CORS (Cross-Origin Resource Sharing) settings are another common issue, allowing requests from untrusted origins and enabling malicious websites to exploit authenticated sessions.

6. Lack of Rate Limiting

Without rate limiting, APIs are vulnerable to brute-force attacks and overwhelming traffic. Attackers can send excessive requests, leading to Denial of Service (DoS) conditions or unauthorized access through systematic guessing of credentials or resource identifiers. Additionally, APIs with cost-per-request operations (like sending SMS messages) can rack up significant expenses if abused.

7. Mass Assignment

Mass assignment happens when APIs automatically bind client-provided data to internal object properties without filtering or validation. Attackers can exploit this to modify or assign unintended properties. For instance, including "isAdmin": true in a request, could grant unauthorized admin privileges.

8. Insufficient Logging and Monitoring

Without proper logging and monitoring, detecting and responding to attacks becomes difficult. Poor practices, such as not recording login attempts or access to sensitive resources, allow attackers to operate unnoticed. Without real-time alerts, organizations may remain unaware of breaches until substantial damage has occurred.

9. Cross-Site Request Forgery (CSRF)

CSRF attacks trick users into performing unintended actions on APIs where they’re authenticated. This usually involves a malicious webpage that sends unauthorized requests, taking advantage of the browser’s automatic inclusion of authentication cookies. For example, a hidden form on a malicious site could trigger a funds transfer or account update without the user’s knowledge.

10. . Denial of Service (DoS/DDoS)

DoS and DDoS attacks overwhelm APIs with excessive requests, making them unresponsive to legitimate users. A simple DoS attack may involve thousands of requests from a single source, whereas DDoS attacks utilize botnets to flood services at scale. Beyond causing outages, these attacks can lead to costly auto-scaling in cloud environments and may act as distractions while attackers exploit other vulnerabilities.

With fewer than half of enterprise APIs expected to be actively managed by 2025, these attacks underscore the importance of robust API security measures. As organizations expand their API ecosystems, maintaining visibility and control becomes increasingly challenging, creating opportunities for attackers to exploit weaknesses undetected.