renanivo

Adds some Multisite-specific functions to WordPress’ XML-RPC interface (http://yourdomain.com/xmlrpc.php).
Using this plugin, you can create a blog, update the archived status and get a blog ID using a remote software (another server, a desktop software, a mobile software…)
The functions enabled by this plugin are:
<ul>
<li>Create Blog (ms.CreateBlog)</li>
<li>Get Blog Id (ms.GetBlogId)</li>
<li>Update Archived (ms.UpdateArchived)</li>
</ul>
refer to the <a href="http://wiki.github.com/renanivo/WP-Multisite-XML-RPC/" rel="nofollow ugc">wiki</a> for further documentation

Multisite XML-RPC

Adds some Multisite-specific functions to WordPress' XML-RPC interface.

yehudah

multipie ways to help block xmlrpc attacks.
This plugin have this options:
First Option: 
Log errors and access – to debug plugin errors and access to the xmlrpc file.
The protection options:
<ul>
<li>Disable xmlrpc – disable the file complete with wordpress built in option.</li>
<li>Block login errors ip’s in htaccess – every WRONG login attempt will be blocked inside the htaccess file.</li>
<li>Enable xmlrpc for a specific user – give permission to access the file to pre define user you will choose.</li>
<li>Disable xmlrpc built in functions – xmlrpc have many options and actions to query on your wordpress site, with this option you can choose which option to disable and wich to keep enabled.</li>
</ul>

xmlrpc attacks blocker

multipie ways to help block xmlrpc attacks.

Multisite XML-RPC vs xmlrpc attacks blocker