1st One : Platinum SEO Pack

Platinum SEO Pack is a WordPress seo plugin. This plugin make your links more foundable and more useful. Also this plugin Redirect your old urls to new one with Redirect 301 rule. If you change any link of your posts Platinum SEO Pack follow your new link and change it with new one.

Plugin Site : Platinum SEO Pack

2nd One :  WordPress Firewall

WordPress Firewall can warn you about hacking attemps and improve your WordPress security.

Plugin Site: WordPress Firewall

3rd One : Wp-Spam Free

This plugin block spam comments. You can add some spam emails into settings. Powerfull than Aksimet.

Plugin Site: Wp-Spam Free

4th One : Wp-reCAPTCHA

This plugin adds reCAPTCHA from recaptcha.net. This plugin improve your comment forms security.

Plugin Site: Wp-reCAPTCHA

5th One : Google XML Sitemaps

This plugin generate a sitemap for Google, Yahoo, Bing and the other services. And this plugin automatically ping this services.

Plugin Site: Google XML Sitemaps

6th One : WP Security Scan

This plugin scan your theme files for viruses. And shows some securtiy errors to you.

Plugin Site: WP Security Scan

7th One : WP System Health

Adds a comprehensive overview and analysis tool into your dashboard to get a single point information about PHP and WordPress internal states and configuration.

Plugin Site: WP System Health

Have a nice day!