Protecting your WordPress site becomes important pretty quickly normally. Sadly it seems many people, and bots, are keen to find a way on to your site if they can, presumably to spread Malware and Spam, but really who knows why else they bother? I’ve been using the free version of WordFence for quite some time and find it pretty efficient and painless. It deals with the vast majority of issues without involving me, and gives me a nice summary along with any important details I might need to know to take further action.
Another plugin I install almost immediately on any new site.