What you do or dont do with p2p is not for me to get into, I'm just saying... if you dont want to share stuff via p2p, you have 2 options.
1. Do not use p2p applications
2. Use p2p applications but configure them to specifically disable sharing on your part.
And again, you're asking about an IP blocker. This assumes you know where your attack or request is coming from and you want to block that request. If you avoid p2p altogether, you dont have to know where it comes from. In any case, like I said before, Gufw may be what you need.