ParaView for Windows from paraview.org doesn't have a signed Publisher
If you download ParaView for Windows from paraview.org Microsoft Defender Smartscreen gets angry because the publisher is shown as an Unknown Publisher. In some organizations they have a policy that just prompts you and lets you run anyway, in others they might have it disabled so you cannot run it. The package needs to be built with a certificate and registered with Windoz and build up a reputation so it will stop prompting once it hits the right count.