1. WP Security Scan is a scanning plugin that will look for any vulnerability in your blog.  This is one of the first steps you can take to protect your WordPress blog from attacks of all kinds.  Once you know where your vulnerabilities are, you can protect against them using a number of other plugins.
2. Admin SSL is a great plugin that makes all pages and areas using passwords to use private or shared SSL or secure pages.  You will need to have a SSL certificate installed.  For more information regarding SSL certificates, contact your web host.
3. AntiVirus plugin works similarly to the antivirus software you likely have on your desk top or lap top computer.  It protects the WordPress blog from any malicious programs that try to detect vulnerabilities, inject malicious code or spam your blog.
4. SI Captcha is a plugin that adds captcha symbols into the forms as needed.  You can add them to comments, registrations or both.  When using these forms you will need to type in the word that appears distorted.  Bots are unable to discern the actual word and this prevents them from sullying the blog with signs ups, links and spam.
5. Invisible Defender is a plugin that reduces the threat of bots signing up, commenting and littering your blog with spam.  If a bot is detected after installation they are not allowed to sign up or post and they are redirected to an error page.  The 403 Forbidden page is where all bots will be directed to, keeping your blog spam free.
6. LogIn LockDown is a plugin that records the IP address of failed attempts at logging in.  If there are multiple attempts within a defined amount of time to log in unsuccessfully the block of IP addresses will be blocked, preventing forced password retrieval leaving your blog open to malicious content and hacking.
7. Maximum Security is an all inclusive program that protects a number of different threats.  It boosts your firewall to protect against malicious attacks as well as spam.
8. WP Sentry is a plugin that manages privacy settings so you can have a portion of your blog or the entire blog private.  It requires user groups to be maintained so that you can assign permissions.  Sensitive topics can only be seen by those user groups and you can prevent indexing of the posts as well.
9. Askimet is a spam protection program that is highly recommended and developed by the makers of WordPress itself.  It checks comment posts against an up to date database of spam references to see if the comment is spam.  If it is not, it is posted or you can choose from a number of options for when spam is detected.  Askimet is updated regularly so that all spam instances can be caught quickly.
10. BackUp WordPress is a plugin that allows you to backup your WordPress blog so that if there is a problem or a disaster you can recover it from the last date of backup quickly and easily.  This is a great way to prevent starting from scratch is something disastrous occurs.

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