When you’re responsible for the security of a site, it’s important that you understand about Bruce Force Attacks. These attacks happen when a number of people or a single person with a number of computers under his or her control tries to access your site multiple (hundreds or thousands of times) in order to try many different password combinations to hack your site.
Over the last couple of months we have seen an increase in brute force attacks from WordPress sites, and this article from WP Beginner can help you take some steps for protecting your site.