How did an unidentified person create user folders on my NAS and network drives on my PC and how can I solve this?

I just discovered (don’t know how long those folders have been present) but I know for sure I did not create those.

I have a QNAP NAS with one networkdrive which I use for storage at home.

Today I found out the following network drive folders: fock1 and leon1and in my homes folder where I keep my own and my wifes folders there was a folder fuck_you27 (think that was the credential folder of the culprit) which I deleted.

For the mapped network drives I am unable to delete those since I don’t seem to have the user credentials for those…

Took a screenshot of the user folder in my recycled:

How do I solve this?