What is the function of AppArmor in a Linux system?

AppArmor is a security module for the Linux kernel that is designed to enhance the security of applications by enforcing restrictions on their capabilities. It works by using profiles, which are sets of rules that define what resources a program can access and how it can interact with the system. Each application can have its own set of rules, allowing for fine-grained control over its behavior.

The primary function of AppArmor is to run applications in a confined environment, limiting their access to files, network resources, and other system components based on the specified profile for that application. This approach helps to minimize the potential damage that can be caused by a compromised application, as it restricts the application's ability to perform malicious activities.

In contrast, the other options describe different functions that are not related to AppArmor's role. For example, encrypting sensitive data would be handled by tools designed specifically for encryption, managing user authentication is performed by authentication systems, and providing firewall services is typically the responsibility of firewall applications or modules rather than an application confinement tool like AppArmor. By focusing on restricting program capabilities, AppArmor plays a crucial role in the overall security model of a Linux system.