Currently there are a few anti viruses on the app store, but most of them focus more on your privacy settings and theft protection rather that protecting your device from actual viruses. They can also be a big drain on your iPads battery. if you use Facebook and twitter a lot I highly recommend installing the free McAfee or TrendMicro anti virus and letting it adjust your privacy settings and then uninstall it once its done, because thats all its good for at the moment.