How can i block these requests

[nilesh]

I am getting following access.log: and are significant in number
RequestMethod=- RequestURI=- HTTPStatus=400  BodyBytesSent=0
RequestTime=0.000  ResponseTime=-  HTTPReferrer="-" UserAgent="-"
X-Forwarded-For=- HTTPStatus=400

Does anyone know why i am getting these empty requests, and how to stop
them.

Posted at Nginx Forum: http://forum.nginx.org/read.php?2,232321,232321#msg-232321