Botnets are generally used for DDoS attacks, bit coin mining or spam email campaigns. If someone is going to steal your bit coins they will most likely target the bitcoin exchange if you use one or wallet with malware. Layered defense is always best. I use CyberReason RansomFree (Free), Microsoft EMET(Free) and also a paid AV suite. I also have a perimeter firewall and perimeter malware scanner, but I'm a little paranoid.