http://wordpress.org/extend/plugins/secure-wordpress/
http://wordpress.org/extend/plugins/exploit-scanner/
http://wordpress.org/extend/plugins/tac/
http://wordpress.org/extend/plugins/update-notifier/
http://wordpress.org/extend/plugins/wordpress-file-monitor/
http://wordpress.org/extend/plugins/wp-malwatch/
http://wordpress.org/extend/plugins/wordpress-firewall-2/
http://wordpress.org/extend/plugins/block-bad-queries/