Storage encrypted suddenly

Hi everyone

I have a strange problem with my xperia M. Somewhen today the Play Store and some other apps crashed so I decided to reboot. The last reboot is about thre days ago. After startup i got a starnge screen asking me for a password to unlock the storage. I have absoltely no idea what this screen is as I have never seen it before. I attatched a screenshot of the phone.
I have never entered a password to encrypt the data on that device. After trying around a bit I called the sony support. They told me to reset the phone using the sony software. But doing this will delete all my data

What I can do to get my data back? And why is my phone suddenly encrypted?

I use Stock ROM think it was 4.2.1 or something. Locked Bootloader not rooted.

Rgds
gentooMueLLe

edit:The time shown on the password screen is not my local time. this is also a litlle bit strange to me

Hi folks

thanks for your replies. I am absolutely sure that I have not actively encrypted the device. I think the process of encryption takes several hours what I should have recognized.
Is it possible that some kind of virus has encrypted the device?

paper13579 said:

As far as i know, it is impossible or really hard to get a virus on a phone

Sent from my C2004 using xda app-developers app

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Thats also my oppinon. for that reason I dont have virus protection software or something similar on my device. As I even have not installed anything since the last reboot I cant imagine that there is a virus on my phone.

Is it possible to encrypt the device remote. I think my google account was hacked, as my password was not valid anymore....
I have never thougt about encryption, so I dont know much about this topic.

Thanks for your help