I just noticed on my main boot drive, in the sharing and permissions section. Their is a user named ''unknown'' This unkown user has read only permissions, and is grayed out. I have tried removing this user by clicking the minus sign. It has no effect. I cant change their privilege level either. I can do this with the other users listed. The ones that aren't grayed out. This (unknown) user is not listed with the rest of the users. Found in the sharing options, under system preferences. In fact all sharing options are turned off. I don't have a wireless network, nor do I run time machine. Even when I click on info, for general files and folders. This unknown user is not present. I can only find this user on the main hd. I have ran permission fix, from disk utility. I even logged in as the root user. To try and change or delete this mystery user, to no avail. Has any one else experienced or seen any issue like this? Should I worry or be concerned?