It doesn't seem to have been mentioned on the forums, which is alarming, but the correct response to finding out your machine has been owned is to shut it the fuck down . Right away. Then boot up a rescue CD, which will have a known working system (read: not compromised), from which you can do some forensic work to find out how you were owned and what data is recoverable. Take the data you can recover offline and the…
well, when wannacry was around, you could "salvage" the decryption key from an infected machine before it was rebooted. not saying your idea is bad advice but you need the full picture to counter ransomware attacks
dd if=/dev/mem of=~/mem.img
to obtain an image dump which may contain the decryption key.