[ubuntu-za] Stop outgoing traffic to specific host

[Wikus]

Hi Guys ,

I have continues traffic to a site that should not be receiving data 
from my pc ( HUBBARD.CLUB.CC.CMU.EDU , 128.237.157.136 )
When I view my traffic with iftop my pc is continuously sending data to 
that address.

Can someone please explain to me in plain easy steps how I stop my pc 
from sending to that adress ?
I have never done this before and have no idea where to start.
Ubuntu 12.04.3 64bit with all updates.

Thank you

- Wikus

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