Files gets automatically copied

Hello, I have a kind of problem here and I need your help......
my flash drive must have some virus which keeps my files hidden and I have to click the show hidden file option in view. i copied the files and checked them and deleted them from recycle bin also. but somehow my friend got access to them.

now I want to know is there any automated system which keeps a copy of those files (or the hidden files)

I yes how to deactivate it and where to those copies are saved?

Please help me with this....