Wordfence - Comprehensive security plugin for WordPress.
WordPress Security Scanner - Check if your WordPress site has known vulnerabilities
iThemes Security - Security plugin that provides over 30+ ways to secure and protect your WordPress site.
Antibot Cloud - PHP Software and Cloud Based Service to protect PHP websites from bad bots and parsers: reduces the load on the server, protects against spam, hacking and searching for vulnerabilities, parsers, brute force, hit bots, theft of content and proxy site…
NinjaFirewall (WP Edition) - A true Web Application Firewall to secure and protect WordPress.
WP Time Capsule - Update your WordPress sites with confidence.