Phone was totally taken over, steps to prevent this??

Plakopaas
edited January 10 in General Topics

Recently my phone was compromised and they got total control of my phone ( could see my screen, listen to my mic, see all my typing, they could command it). I know these people personally so it was a targeted attack and not a random infection. They never got my phone physically so I guessed it was just software and I did a factory reset, I bought a vpn and bought Bitdefender. I am not really technical so I have 4 questions, if anyone could answer I would be very grateful.

1) Did the factory reset wipe this malware/spyware?

2) How is it even possible to get so much power over/ access to someone's phone without taking the phone? My personal guess is whatsapp or email attachments? Why did my free spyware detections app detect nothing?

3) If someone were to pay my mobile data provider, could they enter my phone that way or can they just see my internet history? I know a VPN blocks the viewing of my internet history, this thats why I bought one. But hypothetically could spyware/malware be installed via my mobile data provider?

4) Does Bitdefender even defend against this? When I scan for malware it says it is only scanning my apps. Does Bitdefender even scan other files I downloaded? I am really paranoid about things like e-mail attachments.