Evan Solomon

When you click links, your browser sends referrer information to the site you land on. This is how you get things like referrer counts in Google Analytics. Sometimes, though, you don’t want people to know where you clicked their links from. By default, this plugin will hide your referrers for links from <code>wp-admin</code>. You can also use it to hide links on the front end of your site by making a plugin along the lines of this.
<pre><code>add_action( 'wp_enqueue_scripts', 'es_anonymous_admin_links' ); </code></pre>

Anonymous Admin Links

Hide the referrer for external links in wp-admin using href.li

wplabs

Hide Referer for WordPress removes the referer (referrer) from all external links on your blog. It does this by converting all outgoing 
links on your blog using the href.li service and effectively hides your site as origin of the referred link.
For example, Hide Referer for WordPress will convert an external link to wordpress.org, to <a href="https://href.li/?http://wordpress.org" rel="nofollow ugc">https://href.li/?http://wordpress.org</a>.

Advanced WP Hide Referer

Hide Referer for WordPress removes the referer (referrer) from all external links on your blog. It does this by converting all outgoing

Anonymous Admin Links vs Advanced WP Hide Referer