If you are referring to something like the XML Quadratic Blowup Attack attack vector (see below) then yep then this code will protect against that. This newer Bonus Custom Code may also may be what you are looking for: http://forum.ait-pro.com/forums/topic/post-request-protection-post-attack-protection-post-request-blocker/
Special Thanks goes out to Gary Gordon for bringing the recent WordPress XML-RPC DDoS Exploitation Attacks to our attention, which got us moving on creating this WordPress XML-RPC DDoS Protection code below ASAP.
Protects against the XML Quadratic Blowup Attack as well as other various XML-RPC exploits