Which service is associated with the use of predefined apps in cloud firewalls?

The correct answer, which highlights the association with predefined apps in cloud firewalls, is popular cloud-based services. This choice accurately reflects the functionality of cloud firewalls that utilize sets of predefined applications to simplify and strengthen network security.

Cloud firewalls are designed to automate security policies for widely used applications across various platforms. By having predefined definitions for popular cloud-based services, organizations can implement streamlined security measures, allowing for improved detection, control, and reporting of traffic related to these services. This not only enhances security but also aids in compliance with organizational policies, making it easier for IT teams to manage risks associated with cloud usage.

While other options like open source applications, Microsoft Office applications, and social media platforms might be relevant in specific contexts, they do not encapsulate the broader range of predefined applications that cloud firewalls specifically target. Cloud firewalls are most commonly set up to account for various widely adopted cloud-based services that businesses utilize regularly, thus optimizing their security posture across the board.