Bizarre hacking

Found something strange on my home fileserver a while back - a couple of directories and a few dozen files had appeared that have nothing to do with any of us... I guess someone has either hacked into the server from outside using broadband, though the firewall setup really ought to stop that, or someone local has hacked into it through the wireless network. We have a reasonable security setup but I imagine that just means it takes 'em a few minutes longer, gah.

The strange thing is that the files were just nonsense, I would have expected something constructive (in their terms at least) like an attempt to use the server to spam the world, or something destructive like planting a worm, virus, or embarrassing files... Why would you hack into something and then leave an obvious trail? Bizarre.

Perhaps the file-server is becoming sentient, and these are its birthing cries...