[CentOS] block port forwarding?

Hello,

 i have internet usage rules for all of my network.
only 2 servers have full access to the internet..
lately i've noticed that lots of traffic being produced by the servers ..
is there a way to know whose using port forwarding to my server so they access the internet ?
or is there a way to block people from doing such a thing ?
 		 	   		  
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