Recently WordPress blogs are targeted by attackers and they are using more than 90000+ different IP addresses to launch attacks. This attack is targeted to WordPress login page to gain the access your WordPress admin area. By default WordPress does not block failed login attempts IP address and this allows attackers to try numerous username and password combination. If you are using WordPress, it is highly recommend you can following security measures:
 Upgrade your WordPress version to latest version
 Upgrade all your plugins and themes to thier latest version
 Install security plugin like Better WP Security and other addition security plugins. This is necessary to block failed login attempts.
 Use strong password for your WordPress admin area
 If you are using default “admin” user, it is highly recommend that you create another user and remove default “admin” user
 Scan you website using the anti virus application provided by your hosting provider. If you are using cPanel, you should see “ClamAv Scanner” in your cPanel. Most of the hosting providers offer this in their hosting control panels.
Though the above mesasures will not protect your blog 100% but it will certainly help you to reduce the attacks and will protect your blog.