User mode antivirus software in the Android world

security posture user with a mouse

The purpose of this article is to delve into the details of the current state of user-mode antivirus software in the Android world. We will explore what an antivirus is, the differences between Android and other operating systems, the limitations and capabilities of user-mode antiviruses, and the added benefits of delving deeper into the inner workings of an Android device.

What is an Antivirus and Why is it Important?

An antivirus is software designed to detect and remove malware. The primary function of an antivirus is to protect your device from malware infections and prevent unauthorized access to your data and system resources. Antivirus software typically performs its job by scanning your system for known malware signatures or patterns, analyzing suspicious behavior or code, and blocking or quarantining any malicious files or processes detected.

The importance of having antivirus software on any device cannot be overstated. Malware infections can result in theft of personal data, significant damage to the device, and many more undesired effects. To achieve the desired impact, an antivirus must be implemented with appropriate system visibility and privileges. Depending on the platform, most antiviruses would either be implemented in user-mode (as a standard application) or kernel-mode (at a kernel level of operation), sometimes even as a combination of the two.

User-mode Antiviruses in Other Operating Systems

User-mode antiviruses are common in other operating systems, such as Microsoft Windows or various Linux distributions. However, their impact on Android is much more limited. This is due to the fact that the limitations imposed by Android on user-mode applications are much more restrictive than those in other operating systems.

For example, in Microsoft Windows, user-mode applications may have direct access to system resources and can scan and monitor any activities that take place on the system, as long as the user has granted them sufficient privileges. This level of access allows antivirus software to detect and remove threats in an efficient and thorough manner.

On the other hand, Android's security model is designed to restrict third-party applications from accessing other applications' internal storage or memory and prevent interaction with the core operating system directly. Android assigns a unique user ID (UID) to each Android application. When the application is executed, a process will be spawned with the privileges of the corresponding UID. This UID separation means applications run in isolated environments, more commonly known as sandboxes. By default, apps cannot interact with each other and have limited access to the OS. As a result, user-mode Android antivirus software may not have the necessary privileges and visibility required to detect and remove more sophisticated types of malware or to fully protect the system from various types of threats.

The Capabilities of an Android User-mode Antivirus

Despite the limitations we have gone over, user-mode antiviruses are still able to provide some important security features, with the condition of having appropriate permissions:

  1. User-mode antiviruses may alert about the security impact that external interfaces can have on the device. An example of this is alerting when connecting to WiFi networks that have lower security levels, or informing the user about a webpage with a non-trusted certificate.

  2. User-mode antiviruses may scan apps and files for malware and viruses, both on demand and upon installation as new apps are installed or updated. This is useful, for example, when installing apps from a source other than the Google Play Store (which implements its own static analysis).

  3. User-mode antiviruses may monitor system components, such as the ARP table, and provide detection and mitigation for common attacks related to these components.

These features provide a solid line of defense but fall short in the face of more sophisticated threats that may utilize layers beyond the Android Operating System.

The Benefits of Kernel-Mode Antivirus

The Android Operating System (OS) is built on a modified version of the Linux kernel, which offers strong security features and efficient memory management. However, this also means that every Android device is susceptible to vulnerabilities in parts of the Linux kernel that user-mode antiviruses cannot access. User-mode antiviruses are confined to the Android OS boundaries and cannot detect and handle malicious files that reside in more limited locations in the device file system, even if running with the most privileged account possible (System).

Kernel-mode antivirus software has a higher level of access to system resources, allowing it to perform more advanced scanning and detection techniques, such as scanning process memory and monitoring system calls.

Overall, user-mode antiviruses can be a useful part of a comprehensive Android security strategy, but they should not be relied upon as the sole means of protection. It is important to use other security measures, such as keeping the device and apps up to date, avoiding suspicious downloads and websites, and using strong passwords and authentication methods.

The limitations of user-mode antiviruses are well-known, and adversaries constantly search for ways to embed their tools in deeper, less inspected areas of the device. Being part of the underlying OS, Kaymera gains the powerful position of being the enforcing authority in the device. It can monitor for dangerous permissions requested by apps, such as microphone or camera permissions, and generally provide all the data it needs to keep your device and data secure.