Not a virus. It's hidden from
nautilus (default Unity GUI filesystem browser) by default. It's visible when you navigate using Terminal (do
ls -h to include hidden files when listing).
It's a directory where files are put when you delete it via GUI, so you can restore files when they are deleted this way, but not when you do it via Terminal (i.e.
rm $FILE or
rm -r $DIRECTORY; they're essentially gone forever).
Read How to prevent Ubuntu from creating a .Trash-1000 folder when deleting files from a USB flashdrive? for more information about the
.Trash-1000 folder and how to stop it from being created.
In summary, the link I included mentions:
Don't use the Delete button only (Otherwise the .Trash-1000 folder
will be created)
Press the key combination Shift + Delete together to delete then Ubuntu
won't create a
(Note: If you delete files and folders this way they are gone forever!)
You can safely remove
.Trash-1000, preferably via Terminal (run
rm -rf .Trash-1000).