Today I was checking if there are any updates on Mac App Store and look what type of message came out. What do I need to do ?
Check your internet connection. This could happen for example if you're connecting through a corporate network or wireless hot spot that proxies all traffic through a central server.
If you are using your normal internet connection, where OS X Update usually works, and this is the first time you get this error message, it could be a cause of concern.
Seems to be a problem on Apples side.
Just read this article on MacRumors.