Wordfence - Comprehensive security plugin for WordPress.
Sucuri - Website Protection, Malware Removal, and Blacklist Prevention
MalCare Security Service - The “Only” WordPress Security Plugin with “Instant” WordPress Malware Removal.
iThemes Security - Security plugin that provides over 30+ ways to secure and protect your WordPress site.
Website Scanning Tools - Website Scanning Tools monitor and cleanup your site.
Jetpack - Jetpack offers SEO and security plugins for Wordpress.