Shade Sometimes when I asked here or on other platform about an app not being safe, some people tells me to just install the app without network permission. is that safe enough for security and privacy?
Some examples of things that apps can do without access to a network:
If you grant an app the accessibility permission, then it can display anything on the screen, block your inputs and do any inputs itself. In other words, it will be able to control your device and conceal from you what it is doing. Blocking the app from connecting to any network isn't going to prevent this.
An app can open a link in the web browser or a custom tab, which the Network permission will not prevent it from doing.
A keyboard app can type things into apps itself
An app can insert metadata into other files that you give it.
An app can share data with another app if both apps "agree" to it. For instance, an app developer that makes several apps could easily enable those apps to communicate with each other. This is common for apps used in corporate settings, where the sharing of data, settings, etc. between the developer's apps makes the end-user experience smoother.
If you give data to an app that wants to leak or exfiltrate that data, but is prevented from doing so because you disabled its Network permission, and it is not doing any of the above, it can still send that data away if you ever accidentally or momentarily enable the Network permission for it. For example, last time I checked, when you restore an app with Seedvault it will have the Network permission enabled.