Yes, you can, and yes this will definitely cost extra.
Resources like this cost a provider somewhat heavily, so you can expect this to be a good deal extra, if the provider offers it. I know Ramnose does, and many others as well
Yes you can get the VPS protected with malware and DDOS attack.Some hosting providers charge extra to provide the protection.Where as some hosting providers like ctrlswitches.com provide free protection against such attacks .
In my opinion, you should check if the provider provides Hardware DDOS protection so that you can opt in for that when you are in heavy attack. ForSmall level of attacks you can sign up with Cloudflare or sucurri which will help you normally. If your domain is always prune to DDOS attack, then you can opt in for the hardware firewall DDOS protected VPS
Services provided by each host differ.Some host do charge extra for providing protection and some don't.So check out for the host who provide protection for free or at low cost if you are looking for services at affordable rate.