You need to block all users from uploading data files into risky collaboration applications.

A real-time policy is a type of policy in Netskope’s CASB that allows you to control the actions that users can perform on cloud applications in real time. You can use a real-time policy to block all users from uploading data files into risky collaboration applications by specifying the following elements: the application category (such as Collaboration), the activity (such as Upload), the file type (such as Data), the risk level (such as High or Very High), and the action (such as Block). A DLP rule, a DLP profile, and a block notification are not sufficient to accomplish this task, as they are either sub-components or outcomes of a real-time policy. References: Netskope Security Cloud Operation & Administration (NSCO&A) - Classroom Course, Module 5: Real-Time Policies, Lesson 1: Real-Time Policy Overview and Lesson 2: Real-Time Policy Configuration.