What is App Hardening and Why is it Important for Mobile Security?

Security is at the top of any developer's priorities. Whether it's to protect intellectual property or sensitive user data, being proactive about app security is pragmatic and necessary. 

Enter app hardening, a method that enhances an app’s security to prevent unauthorized access and alterations to an app’s code. 

An app’s code is vital to it functioning correctly and has intellectual value, as it takes time and resources to develop properly. 

But security flaws are not uncommon. In one report, as many as 72.7% of apps in 2024 had at least one security flaw. Mobile app hardening is one way to address these potential weaknesses. Here, we dive into the process, why it’s so important, and techniques to apply.

App hardening is a series of security measures that prevent malicious actors from accessing, tampering with, or reverse engineering an app's code and using it for illicit purposes. 

Unlike systems hardening, which focuses on secure coding during the development stage, app hardening takes place after an application has been developed.

The process uses a combination of hardening techniques that work together to prevent potential hackers from reading or altering code and gaining unauthorized access to user data. 

You can involve different members of your DevSecOps team in the process. Each team member contributes their relevant skills to spot vulnerabilities, ensure codes are secure, and implement necessary hardening techniques.

Today, the majority of app users rely on mobile phones to access their app of choice. It means our devices are handling more and more sensitive data, from authentication credentials to personal and financial details. 

Many app developers and service providers have started implementing security measures that require users to go through a two-factor authentication or take a selfie with ID capabilities to verify their identification. And these can be incredibly effective.

But at the same time, hackers are becoming increasingly creative with how they bypass security and encryption measures on mobiles, using everything from keylogging to debugging software to steal information. 

Data breaches can have serious consequences, resulting in financial loss and a damaged reputation. App hardening ensures your app can defend itself (and users) against various threats, ensuring data integrity, user privacy, and the overall security of a mobile device.

Maintains Brand Image

Building a positive reputation with users takes time, but a single breach can ruin all of your efforts. Even the smallest compromise can damage your company’s reputation and make customers wary of using your product.

Users must be able to trust that your app is safe to use. For example, if you develop a unified communications app, customers need to know that all of your features are secure, whether they’re messaging colleagues or recording a phone call with a client (learn more about how to record a phone call safely and legally).

Security becomes even more paramount if your app handles sensitive data like healthcare and financial details.

Implementing app hardening techniques to safeguard the safety of this data also safeguards your company from negative consequences caused by breaches.

Prevents Intellectual Property Theft

App code is intellectual property—and protecting your intellectual property ensures you have control over how it is used. It can involve patent infringement, stealing of assets, trade secrets, and creative works. 

Intellectual property theft also has financial consequences, resulting in the loss of business from competitors or unlicensed clones. Ultimately, intellectual property theft undermines innovation and impacts growth. 

Meets Regulatory Requirements

While app hardening is beneficial for all developers, in some cases it’s not just a nice-to-have, it’s a need-to-have. Regulations such as General Data Protection Regulation (GDPR) or Payment Card Industry Data Security Standard (PCI DSS) exist for the safety and security of everyone. 

Implementing app hardening ensures you remain compliant with regulatory requirements in your industry or location. Some of these regulations are required by law, so ensuring compliance is vital from a legal point of view but also establishes trust with your users.

While app hardening techniques focus on preventing attacks, it’s important to look at security from a holistic point of view. So it’s worth understanding the core principles of the app hardening process that keep apps secure. This will also help you better understand the role that each app hardening technique plays.

Prediction

As a starting point, it’s essential to understand where attacks come from. By looking at where previous attacks have occurred, you can better predict hacker behavior. Experienced security specialists can help here, digesting large datasets to see any probing attacks and areas where attackers might attempt to access sensitive information.

Detection

Be proactive by having systems in place that warn of possible attacks and where they’re coming from. For example, you can set up a fraud monitoring system to alert you to any suspicious behavior or potential breaches. Alternatively, you can implement a series of escalating alerts, which give a clear picture of the seriousness of breaches as well as when an attack was successfully prevented.

Prevention

This is where most traditional app hardening techniques come into their own. Prevention steps slow down or prevent hackers from accessing vital information such as an app’s code. Preventing code from being used in ways other than it is intended is the ultimate goal of app hardening, so this is the most important principle out of the three to get right. 

There are many techniques for hardening an app, each adhering to one or many of the key principles illustrated above. For maximum security, use a combination of these.

Obfuscation

One of the most popular—and simple—app hardening techniques, obfuscation makes your app’s code as difficult to understand and reverse engineer as possible. That could mean renaming variables and classes to more cryptic names, including fake conditions to functions, or adding dummy code. Either way, the idea is to make the source code difficult to read so attackers are unable to determine the app’s logic. 

Obfuscation is particularly important for apps that handle sensitive data. And while effective, it won’t impact the functionality of the app. Rather, the modifications prevent a hacker from figuring out whatever they intended to about your code.

Anti-tampering

Attackers may try to alter and use app code for their own purposes. If they successfully alter code, anti-tampering measures will prevent the app from running as intended. 

This method detects and responds to these code alterations, running predefined actions to protect the app’s integrity. If it detects any alterations, the anti-tamper mechanisms take specific actions, such as shutting the app down or alerting your security team. If your app operates in an uncontrolled environment, this measure is particularly effective for maintaining trust, integrity, and functionality.

In-App Keyboards

As we mentioned, cyberattacks are becoming increasingly sophisticated. One such attack is keylogging, which uses a malicious keyboard app or software to detect individual keystrokes. 

Attackers can use these to capture sensitive user information, such as passwords, date of birth, and credit card details. For apps that allow users to make online payments, this is a particularly concerning tactic that’s worth hardening against. 

This is where custom keyboards come in. Rather than the mobile device’s default keyboard, the user would type on a stand-alone keyboard that’s embedded into the application. 

Regulating which custom keyboards can be used hardens the app against keylogging attacks by ensuring keystrokes are intercepted by malicious third parties. You can also choose to limit keyboard inputs to specific types (such as numeric) and disable certain features to enhance security. 

Alternative Resources

Today, many businesses rely on the same major providers for certain services, whether that’s Amazon or Google. If that company experienced a security breach, it would impact millions of people. The idea of using alternative resources is to prevent a single-point failure across the market in cases like this. 

For example, if every small business used Google Voice for business communications, this would make it a prime target for an attack. This may mean more hackers attempt a security breach. In this case, looking for a Google Voice alternative for your business reduces your risk of a potential breach.

Anti-Debugging 

When used for legitimate purposes, debugging software helps software developers to detect bugs in an app's code. In fact, debugging programs are widespread and readily available. 

However, when used nefariously, they can also reveal key areas and elements of an app’s code to potential hackers who can then reverse engineer an entire program or app. This results in intellectual property theft and is also used to identify security flaws.

Anti-debugging is a basic hardening technique that adds special code designed to detect when debugging software is being run. It then responds by causing crashes and other fatal errors that halt an attack.

Jailbreak & Root Detection

“Jailbroken” or “rooted” devices have had factory protections removed, making apps that run on these devices particularly susceptible to security threats. Jailbroken and rooted devices could give some software additional permissions that manufacturers like Apple or Google may have prohibited for security reasons. 

Denying access to jailbroken devices is one app hardening technique, but its effectiveness can vary depending on the user’s mobile operating system.

Open source and closed source code are layers of security to consider. If the code is open source, such as Android, this may compromise the security of the app or device. Closed source code is more secure, but may come at a premium. 

Jailbreak detection triggers the use of additional security protocols to protect the app’s code. Taking these extra precautions denies a potential access route for attackers.

App hardening is one of many practices for enhancing mobile and app security. The end goal is to prevent loss—a loss of data, money, and trust. 

Security breaches can result in fines and lawsuits, damaged reputation that leads to a loss of sales, and reduced trust from your user base that impacts your growth and revenue. 

Actively taking steps to harden an app to potential breaches and addressing security flaws is crucial for avoiding these losses.