With the latest macOS update, Catalina, Apple has made changes to the way it verifies software, taking an app-approach were a security clearance is needed -provided by Apple- before the installation itself is able to run. These are now called notarized apps.
Due to this, users trying to make a fresh Prey install in a Mac computer that is set to allow apps from both the App Store AND identified developers will face the following pop-up that blocks the installation:
What is being done about this
We are working on integrating this new process into our software to ensure Apple can notarize the application and review it without inconveniences.
To clarify, the software itself is still properly signed by us, as direct developers and has not been modified in any way that could have resulted in a false-positive malicious analysis.
This is, actually, an error/alert that indicates that the software is not ready for this new analysis process Apple has implemented, and thus can’t be reviewed.
Steps you can follow to install Prey
Apple has released a profound article for macOS Catalina users detailing these configurations from the user’s perspective. In that article, Apple explains how to install an app that hasn’t been notarized yet.
Taken from Apple's support page:
In macOS Catalina and macOS Mojave, when an app fails to install because it hasn’t been notarized or is from an unidentified developer, it will appear in System Preferences > Security & Privacy, under the General tab. Click Open Anyway to confirm your intent to open or install the app.
The warning prompt reappears, and you can click Open.*
The app is now saved as an exception to your security settings, and you can open it in the future by double-clicking it, just as you can any authorized app.
*If you're prompted to open Finder: control-click the app in Finder, choose Open from the menu, and then click Open in the dialog that appears. Enter your admin name and password to open the app.