Some reading up suggests that the trojan in this case needs the user to manually run it first.
So it is likely masquerading as something else.
I would treat any emails regarding beta access/patches with suspicion.
The hearthstone beta email will contain a key, which you can then enter on the battle.net website.
Either manually log into it, by entering the address - battle.net / eu.battle.net or via the battle.net launcher if you are using that.
Unlike as stated in a recent email that one other poster reported, there is no need to remove your authenticator.
I suspect that curse is not the source in this case, as it has been wrongly accused in the past.