the webmaster of my wordpress blog is showing the following message

"http://naibaat.tv/: Suspected hackingJul 24, 2013
Google has detected that some of your pages may contain hidden text or cloaking, techniques that are outside our Webmaster Guidelines.
Specifically, we detected that your site may have been modified by a third party. Typically, the offending party gains access to an insecure directory that has open permissions. Many times, they will upload files or modify existing ones, which then show up as spam in our index."

any one can guide me what to do now.. and how I can remove this error...