I am clueless as of now. Today my personal laptop got executed with petya ransomware (the first variant, red screen one). Bitdefender did tried to help me, but at the end it failed. Suddenly, I had a BSOD (Blue Screen Of Death) error and then my system rebooted.
After reboot, a fake chkdsk (check disk) ran, which in fact was encrypting my mbr (master boot record) files and at the end it end up encrypting my complete boot sector and there was nothing that could have been done.
And then the petya skull image popped with the ransom note. I did tried universal petya decryptable keys to get back into my system, but none of them worked. At last I had to format my laptop and reinstall the windows.
The question arises, being discovered in 2016, petya ransomware variant 1 can still bypass bitdefender antivirus security. This is really very very weird.
(Bitdefender beta tester 2019/ 2020)