You have a choice of natural deterrents that ants don't like, such as cinnamon, vinegar, mint leaves or solution and cloves. The short fall of these is that the ants will often find a way around it. You a number of contact insecticides, such as the one mentioned. Or you can go to Bunnings and buy some Coopex which you have to make up and spray. Those ants making it back to the nest are groomed within the nest and this kills both lots of ants. I have not found AntRid very effective with our problem ants. But if yours are taing the bait they will carry it back to the nest where the queen will also feed on it and that will destroy the nest.
I would put a few bodies on sticky tape, pop into an envelope and sent of to the local Ag. Dept. Branch. It is a free service and they will tell you what they are and also the most effective control. Most of the ants that enter houses are foreign pest species.
Blue