On a recent trip with a colleague I booted up my Mac and saw in iTunes the usual list of 15-20 other users on the same hotel WiFi, all with their libraries in iTunes open for sharing. My colleague was one of them (computer names are listed). He had a veritable cornucopia of fetish porn. Out of respect I didn't watch his videos but I have to say it was kinda hard not asking him the next day about his fascination with poopie.
So just ensure in iTunes you turn off file sharing, and you don't leave anything in your shared folder (in Finder look under your name for a folder called Sharing) and that should be sufficient for casual WiFi use. I'm not promising you won't get hacked by someone who knows what they are doing, but you have less to fear from these users than you do the casual snoopers.
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I'll just have to remember not to add anything to its library.