Personally, I would suggest something along the lines of AVG. I've used AVG for quite a while and find that it's quite good at fending off attacks.
Alternatively, you could use ZoneAlarm, which is practically built to fend off attacks from hackers and other malicious connections/software. If you truly know what you're doing then I would suggest you try ZoneAlarm first, but only if you feel comfortable with it's complexity. If you'd rather go for something a tad simpler, maybe you should try out AVG first. Whichever you end up choosing should be just fine, but I do recommend you at least try both of them before making a final decision.