http://zqktlw5bf6oycxq6qod452xnvdfcqhfwliz54bkul736g6b454jrk2ad.onion/wiki/index.php?title=Intrusive_Surveillance&action=edit
Simply deleting files is not enough, since deletion only removes files from the directory listing and does nothing to actually remove their contents until they are overwritten by some new file. Whenever the topic of secure deletion comes up, an argument will inevitably be raised as to how many times a file must be overwritten and what must it be overwritten with in order for it to be truly gone.