Minecraft and it's viruses?

My 10 year old loves this game but he has ruined 4 laptops in 5 months with viruses from playing minecraft.
How can I stop this from happening?
What is the best virus protection for this?

For free virus protection use "Avast! Free Antivirus". Also download "Spywareblaster". Its a free program that will prevent him from visiting websites that could give him viruses.

Minecraft doesn't give vriuses maybe he downloaded mods

Minecraft doesn't give viruses, but he can download stuff for the game such as mods, resource packs, ETC. Those can give you viruses (Not all of them, only some of them). But your going to have to choose a way for him to stop downloading ones with viruses, I can't really help with that, sorry.

I have absolutely no idea how or why 4 laptops have been "ruined" in 5 months but I can promise you that minecraft is not responsible.