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Application programming interfaces (APIs) are software intermediaries that allow different programs to communicate efficiently with each other, exchange data, and react to set commands. They make applications accessible to external third-party developers, which makes them simple to integrate, ideal for automation, and enables the application to use the data and features of other apps.

The development of business and web applications is increasingly reliant on APIs, but this expansion has also seen an increase in the use of insecure API implementations that put organizations at risk of hacking, DDoS attacks, data loss, and ultimately financial loss. Understanding the typical API vulnerabilities is essential since the security of your APIs is essential to the success of your business.

How Do APIs Work?

API security focuses on developing strategies and solutions, to understand and mitigate unique vulnerabilities and security risks that APIs may pose. An API basically works in a 4-step process:

  1. A client app initiates a request to an API to retrieve information
  2. The API makes a call to a web server or external program after receiving a valid request from the client app
  3. The server sends a response to the API with the information requested
  4. The API transfers the data to the requesting app

Based on their type, APIs can be split into four categories:

  • Open APIs: open-source APIs that you can access via the HTTP They have established API endpoints, request, and response forms, and are also known as public APIs;
  • Partner APIs: they are APIs exposed to or by strategic business partners. Typically, a public API developer site is where developers can self-serve access these APIs. They will nevertheless need to go through an onboarding procedure and obtain login information in order to access partner APIs;
  • Internal APIs: private APIs which are only accessible by internal users. These APIs are intended to improve productivity and communication across different internal development teams;
  • Composite APIs: they combine multiple data or service APIs. These services enable developers to make a single call to many endpoints. In a microservices design, where a single job may require information from numerous sources, composite APIs are helpful.

Most Common API Vulnerabilities

Due to the fact that APIs can be reversed-engineered and are often accessible via the Internet, ensuring that they’re secure should be crucial. APIs are under the same important network and application security concepts as apps and internal network traffic. Strong access restrictions, data governance, rate limitation, input validation, and threat detection are a few of these crucial security factors.

Any weakness in an API’s security is likely to be discovered and taken advantage of by malicious actors. Recent high-profile breaches have demonstrated that hackers are actively targeting APIs. According to OWASP, a non-profit foundation that has the purpose to make web applications and web servers more secure, these are the most common vulnerabilities for APIs:

1.     Weak Authentication

Authentication establishes the legitimacy of users or devices. There may not even be an authentication mechanism in place when there is weak authentication. Most commonly, these vulnerabilities appear in the context of misconfiguration or improper settings that weaken authentication.

Some examples include weak password complexity, high account lockout thresholds, or relying on API keys as the only way to authenticate. By exploiting weak authentication, threat actors may be able to control the user’s accounts or sessions, steal their data, or even engage in other fraudulent transactions.

2.     Broken Object Level Authorization (BOLA)

BOLA API vulnerabilities occur whenever sensitive fields within an object are exposed incorrectly. This is because the server component relies primarily on the object IDs sent from the client to determine which object to access and fails to completely track the client’s state.

For instance, if a user’s personal data is not securely protected within an API response that is sent back to the user’s browser or mobile device, attackers may use this information to pass as the legitimate user and access the account. Thus, threat actors may disclose, modify, or even delete personal information. This problem is frequent in apps that use APIs. You can check out this article written by my colleague to find out more about BOLA.

3.     System Misconfiguration

System misconfiguration may occur at multiple layers and includes missing security patches, overly detailed error messages, forgetting to encrypt data, or leaving cloud storage buckets open and unsecured. Threats from security misconfigurations can include compromises of internal systems or the leakage of sensitive data.

4.     Injections

Injection vulnerabilities allow threat actors to send commands or malicious data to an API through user input fields, passing them as parameters or file uploads.

Injection techniques used by attackers include Javascript, SQL, NoSQL, and OS command lines. The API’s interpreter circumvents any security and executes the malicious commands when there are injection flaws in the code, such as when client-supplied data is directly linked to SQL/NoSQL, Javascript queries, or OS commands.

5.     Improper Asset Management

Since APIs typically expose more endpoints than conventional web applications, accurate documentation is crucial. Deprecated API versions and exposed debug endpoints are two problems that can be mitigated by properly inventorying deployed API versions and hosts.

In this case the API might be vulnerable if:

  • The purpose of an API host is unclear, and there are no explicit answers to the following questions:
    • Which environment is the API running in (e.g., production, staging, test, development)?
    • Who should have network access to the API (e.g., public, internal, partners)?
    • Which API version is running?
    • What data is gathered and processed by the API (e.g., PII)?
    • What’s the data flow?
  • There is no documentation, or the existing documentation is not updated.
  • There is no retirement plan for each API version.
  • Hosts inventory is missing or outdated.
  • Integrated services inventory, either first- or third-party, is missing or outdated.
  • Old or previous API versions are running unpatched.

Defending Yourself Against API Vulnerabilities

As more companies rely on APIs to engage with clients and partners, API vulnerabilities are typically becoming a bigger problem. As we’ve seen, there are several methods to take advantage of these APIs. You can help defend against them, though, by taking a few easy actions:

1.     Ensure your APIs are well-protected

Make sure that only people with permission can access the system by using strong passwords and other security measures. Use robust authentication techniques, such as MFA methods, and make sure that each user has a unique password.

Attackers will find it much harder to access your API as a result, so make sure to periodically check security precautions to keep on top of the most recent developments.

2.     Test your APIs for vulnerabilities regularly

Before incorporating any user input into the logic of an application, developers must take care to thoroughly verify it. In order to avoid denial of service attacks, you should also carefully manage the volume of incoming requests.

You should also be cautious while building APIs to protect sensitive company information from exposure. Use penetration testing techniques to find any systemic flaws and address them as soon as you can.

3.     Keep your systems up-to-date

Prevention is always the best option. Make sure that you’re aware of any new exploits or vulnerabilities that can affect the security of your systems.

Heimdal® Patch & Asset Management is a solution that will make sure the systems in your company are always updated from trusted sources and free from vulnerabilities. This solution enables you to mitigate exploits, achieve compliance, solve vulnerabilities, and install software anywhere in the world, according to your schedule.

Additionally, you acquire strong vulnerability knowledge that informs you of what has already been fixed and the current liabilities in your environment, enabling you to act fast and take action on specific endpoints if risks are allowed to remain for an extended period of time.

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Wrappin’ It Up

Security is of the utmost importance in the API world. If an attacker can compromise your system by changing a few lines of code, it opens up a number of attack vectors that let them to access data that they shouldn’t be able to.

While APIs have a lot of potential uses for both customers and organizations, they can also be easily targeted by threat actors. Companies need to be aware of the increasing number of vulnerabilities that can affect APIs, and act accordingly to prevent malicious actors from breaching their systems if they want their operations to run smoothly.

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Author Profile

Cristian Neagu


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Cristian is a Content Editor & Creator at Heimdal®, where he developed a deep understanding of the digital threat landscape. His style resonates with both technical and non-technical readers, proof being in his skill of communicating cybersecurity norms effectively, in an easy-to-understand manner.

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