This article was originally published on Licel's insights page. Licel is a global application security company.

The increasing popularity of mobile apps has attracted the attention of cybercriminals. And the inevitable result is a rise in the number of sophisticated attacks.

One particularly insidious type of attack is the zero-day exploit which takes advantage of previously unknown vulnerabilities in apps or operating systems.

In this article, we’ll explore some enhanced mobile app security strategies that can aid in zero-day attack prevention. Armed with the insights below, you can protect your app and safeguard your end users' valuable data and privacy.

OS updates

When it comes to mobile security, keeping the operating system (OS) up to date is key. Both iOS and Android platforms release regular updates to patch security vulnerabilities and enhance overall system stability.

For example, one of the latest system iOS updates patched the critical vulnerabilities in IOSurfaceAccelerator and WebKit. This allows for the remote code execution (RCE) of kernel privileges by manufacturing a specific web page. With the latest security patches in place, you can encourage your end users to update their OS version promptly, which significantly reduces the risk of zero-day attacks.

Sticking with the iOS platform, Apple also provides a robust system called Lockdown mode. This enables a higher level of security by restricting access to sensitive information and features. If you’ve developed an app, then you should definitely educate your users about the benefits of enabling this mode and following the recommended security practices. Lockdown mode was created specifically with a view to protecting individuals more likely to be targeted - or even persecuted - by bad actors. Human rights activists, for example. But it’s a feature that anybody can use if it makes them feel safer on their device.

Android developers have the advantage of utilizing a sandbox model which isolates an app's processes and data from other apps and the underlying OS. To maximize the security benefits of the sandbox model, you should set the targeted SDK value as high as possible during app development. This makes sure that the app is built using the latest version of the SDK, incorporating the most advanced security features and mitigations available.

But OS updates alone aren’t enough to ensure zero-day attack prevention.

If you’re a developer, then there are plenty of other enhanced mobile app security measures you should adopt.

Device Authentication

Verifying the authenticity of the operating system and the device itself is another critical aspect of mobile app security. Android offers a powerful framework called Play Integrity API which enables developers to verify the integrity of the OS and device.

Play Integrity API, the successor to SafetyNet, allows you to perform device attestation. This is the act of making sure that the app is running on a genuine and trusted device. In comparison to SafetyNet, Integrity API can also verify that an application is the very same binary that was purchased or downloaded from Google Play.

Another powerful feature of device integrity checks is security key attestation. Using the API and data provided by Android, you can make sure that your encryption keys are stored securely in hardware and the underlying OS is shipped by Google with the given guarantees. It enhances trust assurance, protects against key extraction, and provides resistance to tampering attempts.

In much the same way, iOS provides the Attestation Framework, which allows developers to authenticate the device and OS.

By utilizing these frameworks, you add an extra layer of protection against unauthorized usage, tampering, and attacks targeting compromised devices.

Implementing device authentication doesn’t only help with zero-day attack prevention. It also stops unauthorized usage on rooted or jailbroken devices. It’s essential that you integrate these authentication mechanisms into your app to ensure the highest level of security (and therefore long-term trust from end users). We covered the importance of device attestation frameworks and integrity control in a bit more detail in a separate article about publishing apps on third party platforms.

So, by leveraging the sandbox model and implementing device authentication mechanisms, you can significantly bolster your app's resilience against zero day attacks. These measures, when combined with other enhanced protection techniques, create a robust defensive system.

With this holistic defensive system in mind, let’s move on to the next step in zero-day attack prevention - data encryption and device binding.

Data Encryption and Device Binding

Data encryption and device binding techniques provide additional layers of protection for sensitive data and strengthen your app's resilience against reverse engineering attempts.

Data encryption

Data encryption plays a crucial role in safeguarding sensitive information stored locally within your mobile app. By encrypting data, you can make sure that even if an attacker gained unauthorized access to the device or the app's data, then the information would remain incomprehensible and unusable.

There are various encryption algorithms and techniques available that you can implement. But remember, it’s vital to choose strong encryption algorithms and employ best practices for key management to maintain the integrity and confidentiality of the encrypted data. You should also consider encrypting data during transmission to protect it from potential interception and tampering.

It’s also worth exploring the option of minimizing data storage on the device. By adopting a "data-not-stored" approach - where sensitive information is retrieved from secure servers when needed and promptly discarded afterwards - you can significantly reduce the attack surface. And as such the potential impact of zero-day exploits targeting locally stored data is also diminished. This approach is frequently adopted by online banks. Their mobile apps often store nothing except for the username of the user.

Both Android and iOS provide developers with tools and libraries to encrypt data at rest, ensuring the confidentiality and integrity of sensitive information stored on mobile devices. And while the overarching goal of data encryption is similar on both platforms, there are some differences in the specific tools and approaches available.

Android offers the KeyStore system, which provides a secure container for storing cryptographic keys and performing cryptographic operations. Developers can generate and securely store encryption keys within the KeyStore, leveraging hardware-backed security if available. The KeyStore API allows for seamless integration with various encryption algorithms and modes, ensuring data confidentiality.

The corresponding capability for iOS is the Keychain Services API. It allows developers to securely store sensitive data, including encryption keys, passwords, and certificates. The Keychain Services API handles key management and provides strong protection for stored data, leveraging hardware-backed security.

Android also provides the EncryptedSharedPreferences class as part of the AndroidX Security library. With this tool you can encrypt shared preferences, providing a convenient way to store small amounts of encrypted data over time.

A set of cryptographic functions and APIs for iOS bears the name of CommonCrypto Framework. You can use this framework to perform data encryption using symmetric or asymmetric encryption algorithms. These include AES (Advanced Encryption Standard) or RSA (Rivest-Shamir-Adleman).

iOS adds data protection by default to all application data after the user enables the passcode on the device. This capability is called Data Protection API - it enables automatic encryption of files and data at rest. By applying appropriate data protection classes to files or directories, you can be sure that the data remains encrypted when the device is locked or in a powered-off state.

It’s important to note that while both Android and iOS provide native tools and libraries for data encryption, there are also additional security measures worth considering. These include secure key management, strong encryption algorithms, and adherence to best practices for secure coding and data handling.

Device binding

Device binding is a technique that helps prevent reverse engineering and unauthorized usage of the app by tying it to the specific characteristics of the device. By establishing a strong binding between the app and the device, you create an additional barrier for attackers attempting to analyze and modify your app's behaviour.

Device binding can be implemented using various methods, such as generating unique device identifiers, utilizing hardware-based attestation, or leveraging device-specific characteristics like device fingerprints. These techniques enable the app to verify the integrity of the device it’s running on and to detect potential tampering attempts.

You should refer to resources such as the OWASP Mobile Security Testing Guide for comprehensive guidelines on implementing device binding in your apps. We also covered it in our guide to mobile application protection as part of our advice for stopping mobile app fraud.

By incorporating robust data encryption techniques and implementing device binding, you can significantly enhance the security of your mobile apps. And this can go a long way in helping to achieve zero-day attack prevention.

That said, it’s important to note that these strategies should be complemented by other protection techniques to establish a comprehensive security framework. And as technologies evolve, there are new and exciting ways to fortify mobile app security against zero-day exploits.

Leveraging Anomaly Detection with AI

As the sophistication of zero day attacks continues to evolve, traditional rule-based security mechanisms may fall short in detecting and preventing these exploits. To augment the security posture of mobile apps and achieve zero day attack prevention, you can leverage the power of anomaly detection techniques based on artificial intelligence (AI).

Let's explore how AI can be utilized for anomaly detection in mobile app security.

Identifying Suspicious Patterns

AI-based anomaly detection algorithms can analyze various aspects of app behaviour, such as the number of requests, payload sizes, and error patterns. By establishing baseline patterns of normal behaviour, AI models can detect deviations from said patterns, which might indicate potential zero-day attacks or abnormal activities.

For example, say an app suddenly experiences an unusually high number of requests or encounters unexpected payload sizes. This may suggest a malicious attempt to exploit a vulnerability. AI algorithms can detect these anomalies and trigger appropriate security measures, from simply logging the event to alerting administrators, or even automatically blocking suspicious activities.

Training AI Models

To implement effective anomaly detection, developers need to train AI models using representative and diverse datasets. This training data should include both normal app behaviour and various attack scenarios. By exposing the AI models to a wide range of app activities, they can learn to distinguish between legitimate behaviours and anomalous patterns that might hint at a zero-day attack.

It’s vitally important to continually update and refine the AI models as new attack patterns emerge. Make sure to keep a keen eye on emerging threats, security research, and the latest industry practices to ensure the AI models remain effective against evolving zero-day attack techniques.

Collaborative threat intelligence

Collaboration within the developer community and information sharing about zero-day attacks can be invaluable in combating them in the long run. By sharing anonymized threat intelligence data, you can collectively build more robust AI models for anomaly detection.

Industry groups, security communities, and threat intelligence platforms each provide channels for sharing insights and indicators of compromises related to zero-day attacks. If you’re a developer and you’re interested in security, then you should actively participate in these initiatives to stay informed about emerging threats. You’ll then be able to leverage this shared knowledge to enhance your own app security.

So, by harnessing the power of AI for anomaly detection, you can augment your app's security defenses against zero day attacks. But it’s important to remember that AI-based approaches should be used in conjunction with other protection techniques mentioned earlier in this article, such as data encryption, device binding, and OS updates. Each of them helps to create a comprehensive security framework.

Zero-day attack prevention strategies

The mobile app security landscape is ever-changing. And so zero-day attack prevention requires a multi-layered approach. In this article, we’ve explored several key strategies that you can employ to fight against zero-day exploits.

One key idea to highlight before the end of this piece is that any attack, regardless of its sophistication, leaves behind traces. This notion challenges the widely-held misconception that zero-day attacks are somehow undetectable and untraceable. By implementing security measures such as data encryption and device binding, you create barriers that make it significantly harder for attackers to exploit vulnerabilities and cover their tracks completely.

What’s more, the adoption of device attestation and anomaly detection with the help of AI introduces proactive defence mechanisms. Device attestation ensures the integrity of cryptographic keys and verifies the authenticity of the device, while anomaly detection employs AI algorithms to identify suspicious patterns and behaviours. These techniques allow for the online detection of zero-day attacks during their active phase, providing the opportunity to identify their traces and prevent further exploitation.

But remember that all of the strategies we’ve set out in this article should be implemented in conjunction with one another. That way individual protection techniques can become something much bigger - a comprehensive security framework. Additional measures like code protection, protection against MITM attacks, and application integrity should be considered to further strengthen app security, too.

As a mobile developer, you must prioritize ongoing education and awareness regarding emerging threats and best practices in mobile app security. Collaborating with industry groups and sharing threat intelligence can make zero-day attack prevention more achievable for all of us.

So, safeguarding mobile apps against zero-day exploits requires a proactive and multi-faceted approach. By making OS updates a priority, leveraging the sandbox model and device authentication, implementing data encryption and device binding, and utilizing AI-based anomaly detection, you can significantly enhance the security posture of your app.

All of us have to continually adapt and evolve our security strategies to keep pace with the evolving threat landscape.

But achieve this goal and the result is well worth it - you ensure the protection of your user’s data and their privacy. And by doing so you gain their long-term trust.

Minimizing the risk of zero-day attacks is all about creating a holistic app security posture. Check out Licelus guide to mobile application protection to better understand how to achieve this goal.