Hello, I have had my new iMac for about one week now, and I could not be happier. I have used only Windows PCs up until now. I am still trying to get accustomed to OSX, and particularly the security settings for my network. I have an Airport Extreme Base Station. Besides turning on the firewall in OSX, what other steps should I take to maximize security? What about with the Base Station? I remember, on my PC, I used to be non-pingable with the Linksys router, but now I seem to be pingable. Is this a potential security risk? Thank you!