Hacking and antivirus

For the first time since I use internet, my pc has been attacked. <Tr>

This morning I noticed a new and strange screen when I tried to access the bank.
I became suspicious and called the customer service from which I had confirmation that it was a scam attempt.
Luckily nothing happened, I had the codes blocked, I sent a message to the police post and I will "disinfect" the pc, but this reminded me that the Internet is always present in danger, especially for us who trade.

I'm not telling you anything new, we all know it, but I think that remembering it does not hurt ... open eyes and better to check if you have even the slightest doubt.

How do you defend yourself? What antivirus do you use? Which one do you think is the best?
I currently have Microsoft Security Essentials, in the past I tried Avast and Kaspersky (but the latter greatly slowed down my PC).