What is API Security for Mobile Apps? Why Is It Important?

Businesses have gone mobile-first, and with good reason—people are spending more time and more money on their phones than ever before. For instance, in 2023, an estimated 66% or 2/3rds of all online orders were made from mobile devices. And in 2024, businesses are expected to spend $402 billion on mobile advertising.

Mobile apps have become the first choice for users for their online activities in banking, e-commerce, media streaming, social media, etc. Increasingly, mobile apps on smartphones ‘talk’ to each other. 

According to a recent study, attacks on APIs have increased by 117% yearly. Even a single user data breach or a few hours of downtime can impact a business to millions of dollars. Businesses can no longer afford to allow the security of their mobile APIs to take a backseat.

Why is mobile app API security important?

We have grown accustomed to personalized and seamless user experiences across multiple apps. APIs power these interactions between mobile apps. 

As mobile apps continue to grow, APIs have become ubiquitous, and their threat landscape has rapidly expanded. 

Here’s why you should consider security for mobile APIs as mission-critical: 

• APIs carry sensitive user information such as login credentials, financial information, personal details, etc. A data breach that compromises personal information can have grave social and economic consequences for thousands of users.
  
• An API can have multiple mobile apps as its endpoints. Attackers who gain access to an unprotected API can disrupt services for a few hours and/or steal confidential user data from multiple apps. Businesses can lose millions of dollars, not to mention the loss of reputation.
  
• A data breach can invite legal action and financial penalties due to non-compliance with data protection regulations such as GDPR, CCPA, HIPAA, etc.

Expert opinion 

Raghunandan J, Appknox's Senior Product Manager, believes that:
"API security in mobile apps is essential to ensure reliable user experiences, maintain the integrity of data transactions, and ensure compliance with industry regulations.

Appknox supports developers by providing thorough security evaluations and continuous monitoring, helping them secure their APIs against evolving threats."

So, what is API security for mobile apps?

API security for mobile apps refers to the processes and tools used to protect the integrity of both owned and used mobile APIs and safeguard against attacks that seek to exploit sensitive data and/or disrupt services.

Security teams now focus exclusively on mobile app API testing and increasingly rely on application security testing software (mostly the SAST tools) to test and secure mobile APIs. 

However, when it comes to their effectiveness in testing the security of mobile app APIs, app security testing software has limitations that make them less than ideal choices as mobile app API testing tools.

• API security for mobile apps refers to the processes and tools used to protect the integrity of both owned and used mobile APIs and safeguard against attacks that seek to exploit sensitive data and/or disrupt services.
• Security teams now focus exclusively on mobile app API testing and increasingly rely on application security testing software (mostly the SAST tools) to test and secure mobile APIs. 
• However, when it comes to their effectiveness in testing the security of mobile app APIs, app security testing software has limitations that make them less than ideal choices as mobile app API testing tools.

The question that then confronts enterprises is, how do we test the security of mobile app APIs? The answer lies in automated application security testing. 

Why should you automate mobile app API security testing?

Mobile app APIs are growing exponentially and becoming more sophisticated by the minute. 

Besides, manually testing a considerable volume of mobile APIs can be tedious and time-consuming, not to mention a huge drain on the security testing team's bandwidth. When it takes time to discover and resolve security vulnerabilities, security testing can hold up the production/release cycle.

In addition, the limitations of manual testing, such as incomplete coverage of APIs in security tests, leave the door open for attackers to exploit API security vulnerabilities. These issues pose a severe challenge to remediating the security posture of mobile app APIs. 

Automating API security testing frees up critical resources and ensures a more robust security posture for your mobile APIs. 

In particular, automated dynamic application security testing, or DAST, offers a practical approach to mobile app API testing as

• A DAST tool tests your mobile applications in run-time, stimulates clicks on every app component on every screen, and triggers calls to all the APIs used by the mobile app. This creates a directory of all API calls made by the app.
• Automated DAST ensures comprehensive security testing coverage and that no API is overlooked. That way, all potential security vulnerabilities are detected and fixed to minimize threat exposure.
• A DAST tool automatically replicates real-life interactions on your app on a wide range of real devices. This overcomes the limitations of emulator-based testing, efficiently identifies potential security vulnerabilities, and delivers accurate test results.
• A DAST tool lets you schedule automated security scans for multiple mobile applications simultaneously, allowing you to perform security tests swiftly and without manual intervention. This accelerates app development and facilitates faster releases.
• A DAST tool performs deep vulnerability scanning to identify security vulnerabilities in your mobile app APIs accurately. The detailed insights from the vulnerability scanning report can help you proactively mitigate security risks.

Watch an on-demand webinar on the best practices of API security testing

What are the threats to API security for mobile apps?

Addressing API security threats is essential to protecting mobile apps from data breaches, unauthorized access, and malicious attacks. Some of the threats are:

• Insecure data transmission

  If APIs transmit sensitive data without proper encryption (e.g., HTTPS), attackers can intercept it using man-in-the-middle (MITM) attacks, leading to data breaches.

• Weak authentication and authorization

  APIs with poor authentication or authorization mechanisms are vulnerable to broken authentication, allowing attackers to impersonate users or access unauthorized features and data.

• Lack of rate limiting

  Without rate limiting, APIs are exposed to brute force or denial-of-service (DoS) attacks, where attackers send excessive requests to overwhelm the server or guess login credentials.

• Insufficient input validation

  APIs that don’t validate inputs properly can be exploited via SQL injection or other injection attacks, compromising the system's integrity and exposing sensitive data.

• API key leakage

  Attackers can reverse-engineer API keys hardcoded in mobile apps, allowing them to access APIs without authorization.

A three-step API security framework for your organization

Adopting an API security framework that everyone in the organization can align on helps contain security threats arising from the increased usage of APIs.

An API security framework outlines simple yet critical protocols related to using APIs. Let’s look at a three-step API security framework you can implement in your organization.

Step 1: Continuous API discovery and specification creation

Continuous API discovery is essential to building and maintaining an up-to-date inventory of APIs in use in your organization. Lack of visibility into what APIs and how many are in use across your organization presents one of the biggest challenges to API security. 

As APIs undergo changes and updates and new versions are released, API specifications must be updated so everyone understands what the API does. 

In short, API discovery and specification are necessary for a comprehensive security assessment of all APIs in use at your organization.

Step 2: Continuous API specification analysis and inspection

The next step entails conducting the right type of security testing: 

• Verifying if the updated API has the right data encryption, 
• Relying on proper authentication and authorization policy, 
• Determining which data sources are being accessed, etc.

This is where API security automation tools truly shine, as they can quickly and dynamically find potential vulnerabilities within the API's authentication and encryption layers.

Step 3: API policy enablement and enforcement

The final step of the API security framework is policy creation and enforcement. This requires answering two questions: 

1. Who should be able to use the API? (ensures fair usage of the API)
2. What level of sensitivity, regulatory oversight, and/or privacy concerns does the API have? (enforce the right level of access control)

Although API policy enforcement was traditionally done at the network gateway layer, cloud and mobile architectures have forced developers to provide security aspects through SDKs and the dashboards of cloud service platform providers.

How to choose the right API security automation tool?

Choosing the right API security automation tool is key to ensuring a robust security posture for your organization.

Consider the following factors when evaluating an API security automation tool for your business:

Accuracy

Your security automation tool should 

1. Ensure complete test coverage of all APIs used in your mobile application and
2. Detect and report all possible vulnerabilities accurately. 

If the results of each API security test show many false positives, your engineering/ DevOps teams will need to filter the results to identify the actual security vulnerabilities manually.

Coverage

The threat landscape for mobile APIs is constantly evolving. You need an API security automation tool that provides comprehensive security coverage against various known threats. 

The tool should ensure preparedness against emerging threats by integrating with threat intelligence databases and receiving real-time updates.

Scalability

When choosing an API security automation tool, account for the possibility that your product offerings will continue to grow. Your security testing efforts will need to scale to secure a growing number of mobile apps, APIs, endpoints, calls, and parameters.

Cost

Your engineering and DevOps teams might have built your security testing tech stack by combining numerous point-solution tools. However, the license costs for multiple tools make security testing expensive. 

A good security testing automation platform consolidates your testing tech stack, replaces multiple disparate tools, and drastically reduces expenses on license fees.

Speed

When mobile API security testing proceeds slowly, discovering and resolving security threats takes a long time. This delays development cycles and time to market and affects the business's bottom line. 

The right API security automation tool reduces the time to complete security tests by

• Automating security scans, 
• Running tests on multiple mobile apps simultaneously and 
• Performing comprehensive tests in one go.
  
  

Automation

Engineering and DevOps resource bandwidth takes a lot of work to come by. 

Manually testing every permutation and combination of API calls, endpoints, and parameters can become a herculean task, and teams simply cannot allocate the time and resources required. 

Automated API security testing is more accurate, helps you cover a larger attack surface in less time, and can ensure a robust security posture against emerging threats through frequent security scans.

Why we built API security testing at the core of Appknox's vulnerability assessment

Mobile app APIs are fast becoming the vector of choice for attackers. Enterprises must identify and resolve security vulnerabilities across their API inventory to safeguard against data breaches and/or service disruptions. 

Here’s why developers and security researchers looking to build safe and secure mobile ecosystems rely on Appknox as their trusted API security testing partner (and why you should, too):

• Appknox combines mobile-first vulnerability assessment, automated DAST, and penetration-testing-as-a-service into one cost-effective, enterprise-grade solution that can form the backbone of your mobile API security testing tech stack.
• Automate testing of mobile app vulnerabilities during runtime on real devices,
• Low levels of false positives (<1%) ensure a highly efficient API security testing process,
• Comprehensive security scan reports that detail the detected issues’ business impact, ways to remediate vulnerabilities and compliance issues,
• Adhere to OWASP best practices for application security testing and
• Comply with data protection regulations such as HIPAA, PCI-DSS, and GDPR.

Appknox’s unique hybrid approach of ‘system plus human’ provides a holistic approach to maintaining a robust security posture. Integrating Appknox with threat intelligence databases ensures your mobile app APIs are safeguarded against known and evolving security threats.

In conclusion, if you are an enterprise looking to take control of your mobile app security, you need not look any further. 

FAQs

1. What is an API in application security?

An API (Application Programming Interface) is like a doorway allowing different apps or systems to communicate in application security. APIs let applications exchange data or interact with services, such as logging in, retrieving user information, or accessing databases.
APIs are crucial for security because they can expose sensitive data if not properly protected. Hackers often target APIs to exploit vulnerabilities, so securing them with encryption, authentication, and other safeguards is essential. A secure API ensures that only authorized users or systems can access the data or functions it provides, protecting the app from breaches and unauthorized access.

2. What are the benefits of mobile app API security?

The key benefits of API security for mobile apps are: 

• Safeguarding user data: API security helps protect personal data, like login credentials or financial information, from hackers. The digital lock prevents unauthorized eyes from accessing sensitive details, ensuring users feel confident using the app.
• Enhancing user trust: Solid API security builds a reputation for reliability, helping businesses establish stronger, long-term relationships with their users.
• Preventing exploits: Secure APIs ensure that only authorized users and devices can interact with the app, blocking malicious attempts to tamper with the system.
• Regulatory compliance: API security helps mobile apps comply with Data protection laws like GDPR and HIPAA, protecting both the business and its users from legal risks.
• Ensuring app stability: API security guards against attacks that could overwhelm or shut down services, ensuring that apps run smoothly and minimizing downtime.

3. How do I secure API authentication and authorization?

Here’s how you can do it:

1. Use token-based authentication

Start by using OAuth 2.0 or JSON Web Tokens (JWT) to authenticate users. They enable stateless authentication, so your servers won’t need to store session data—making the process faster and more efficient.

2. Enforce strong password policies

Add multi-factor authentication (MFA) for another layer of protection. This makes it much harder for attackers to gain access.

3. Use HTTPS everywhere

Always use HTTPS to encrypt all API requests and responses to ensure that data can’t be intercepted while it’s being transmitted, keeping sensitive information safe.

4. Set permissions carefully

Role-based access control (RBAC) gives users access only to what they need. This helps minimize risk by ensuring that only authorized users can access sensitive parts of apps.

5. Rotate and expire tokens regularly

This keeps stolen tokens from being used for long, reducing the risk of misuse.

4. What is a common mistake developers make with API security?

One common mistake developers make with API security is hardcoding API keys or credentials directly into the app's code. This practice exposes sensitive information, making it easy for attackers to decompile the app, extract the keys, and gain unauthorized access to your API and data.
Instead, developers should store keys securely in environment variables or use a key management system to protect them, keeping the app safe from potential breaches.

5. What are the best practices for API security for mobile apps?

Some best practices for mobile API security are:

1. Use HTTPS to transmit data between the app and the API server.
2. Ensure only authorized users access your APIs by implementing secure authentication and authorization methods.
3. Validate and sanitize all user inputs to prevent injection attacks.
4. Control the number of API requests a user can make within a timeframe by implementing rate limiting.
5. Incorporate data encryption in transit and at rest to protect it from unauthorized access.
6. Use API gateways to manage, monitor, and secure API traffic.
7. Fix vulnerabilities in your APIs by conducting regular security audits and code reviews.
8. Address suspicious behavior immediately by monitoring and logging API activity.

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