CopyLink is a WordPress plugin developed by Dejan SEO which places automatic links on text copied from your website.
People copy content from websites they visit and spread it around via email, social media, blogs and other online channels. Content copied from a CopyLink enabled website receives automatic links to pages content was copied from.
Attribution prefix (e.g. Via: or Author: ) can be customised in the plugin’s settings page. CopyLink can also track additional statistics such as: IP address, date, user agent, link and copied content. This information can be stored in the database for future reference. Auto-generated attribution is not forced and can be removed by the end user if they choose not to include the link. Live link option is not available when pasting into basic text editors such as Notepad.
http://wordpress.org/extend/plugins/copy-link/
Here is a screenshot of the plugin statistics page: