I recently purchased Bitdefender 2018 as I was using the free version of Avast for protection but wanted to upgrade to premium. Bitdefender blocks my Steam games from opening as well as causes issues with other online games. From what I could tell in the firewall rules, nothing was really being blocked. However, the rules are quite complicated and I'm not really sure how to use them. I've since uninstalled Bitdefender and reverted back to the free Avast so that way I can play my games while still having some protection. I would like to sort out Bitdefender so that I can use the software I paid for.