Sucuri Sitecheck Free Security Scanner is a WordPress plugin by [email protected], and dremeda that enables full malware and blacklisting scan capabilities from Sucuri SiteCheck right in your WordPress dashboard. It will check for malware, spam, blacklisting and other security issues like htaccess redirections, hidden eval code, etc.
You can also scan your site at http://sitecheck.sucuri.net.
Download: http://wordpress.org/extend/plugins/sucuri-scanner/