I recommend adding a reCaptcha plugin to your site to prevent robots, programs and other scripts from hacking or spamming your site.
To configure one of the many recaptcha plugins, install it to your site and then using Google’s interface (since most of these are Google products) get a key for your domain, bring it back to your site and enter the key from Google in the settings. You can usually choose to enable the protection on just the login page, or also on comment forms, either of these will prevent most scripts from accessing your site.