"SFRK" sounds like a computer name. Is your computer named "SFRK?" If not, then I don't think you have anything to worry about.
Many networks may show up under the AirPort icon in the menubar depending on how many wireless networks are within range of your computer -- but that doesn't mean that you're actually connected to any of them (unless there's a checkmark next to one), and it doesn't mean that any computers on any of those unchecked networks can "see" your computer.
It's basically saying, "Hey, here are some close-by networks that you can elect to join, if you so choose." All wireless networks "broadcast" information about themselves (even ones with hidden SSIDs) so that wireless clients can "find" them and connect to them. I believe this is what you're seeing and it's perfectly normal.
If this isn't what you're seeing or you suspect something else, please explain.