michael_greenberg

PHPEnkoder is a port of the excellent <a href="http://hivelogic.com/enkoder" rel="nofollow ugc">Hivelogic 
Enkoder</a> to PHP and, more specifically, 
to WordPress. It is used to display text in a way that users can see 
and bots can’t.
The encoding system is directly and unabashedly stolen from the 
BSD-licensed source of Hivelogic Enkoder, which works by randomly 
encoding a piece of text and sending to the browser self-evaluating 
Javascript that will generate the original text. This works in two 
ways: first, a bot must first have a fairly complete Javascript 
implementation (in particular, it must have <code>eval</code>); second, the 
decoding process can be made arbitrarily computationally 
intensive. This is similar to the idea of charging computational 
payments to send e-mail, only this is actually implemented.
By default, PHPEnkoder scrambles e-mails in plaintext and in <code>mailto:</code> 
links. It additionally provides a shortcode for manual scrambling, 
used like so: <code>[enkode text="shown to non-JS browsers"]this will be 
scrambled[/enkode]</code>.

PHPEnkoder

Encodes mailto: links and e-mail addresses with JavaScript to stifle webcrawlers.  Automatically turns plaintext e-mails into (enkoded) links.

cgarvey

This plugin lets you use a shortcode to automatically generate ‘cloaked’ email addresses in your content.
What is cloaking? 
Take an email address like barack@whitehouse.gov. If that was to appear on one of your posts/pages, it could easily be ‘scraped’ or ‘harvested’ automatically to add that email address to a spam list of some sort. Cloaking is all about making that harder to do.
How does this plugin do its cloaking? 
For any email address you include in your content, using the custom shortcode of [email barack@whitehouse.gov], that email address will appear as “barack -at- whitehouse -dot- gov” in your content initially. JavaScript running in the browser will then convert that email address to a regular, clickable, email link. Whilst it may seem pointless to convert a regular email address to a strange format only to convert it back again, the idea is that most automated ‘scrapers’, or ‘harvesters’, do not run JavaScript and hence won’t be able to pick up on the non-standard email address. The vast majority of users visiting your site will have JavaScript, and will see regular email addresses (not the strange format).
What about users who have no JavaScript, or have it disabled? 
They will see the strange format (“barack -at- whitehouse -dot- gov”). You can include a footnote using a custom short code [emailnojs] which will explain the strange format, if you wish to cater for that tiny minority of visitors.
<h3>License</h3>
This plugin uses the GPLv3 license.

Email JavaScript Cloak

A simple plugin to use JavaScript to cloak email addresses in your WordPress content (posts & pages).

PHPEnkoder vs Email JavaScript Cloak