If you notice a large increase in the online traffic to your Internet site and in case after you look into the visitor statistics it turns out that it comes from countries across the world or from other web servers, your Internet site is more than likely being attacked by an automatic bot. Such programs go through random websites looking to log in to their admin area by using a brute-force attack or to leave spam comments beneath any sort of article where such an option is offered. The fact is that, that's something quite popular in recent times, but if you know the IP addresses through which the attacks come, you'll be able to block them, so the bots will be unable to access your site in any way. Of course, you'll be able to block IPs even if you allow only people from certain countries to access your website.