I've little to no experience with Apple products dude, unfortunately ; I would suggest a good Anti-Malware program as being essential and, depending on the P2P Program you're looking to use, forwarding the right ports on your Router (If your Modem/Router makes use of a NAT when connecting to the internet) can makes things a little easier too.

Admittedly, this stems from PC-based experience and might not correspond to that of Apple based systems.