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The great command line challenge

Your mission, should you accept it, is to create a single command line program to count the number of emails from each IP Address that has attempted to access my hosts using SSH. Download the file to try your hand at that. Be aware that this file contains more than 50,000 lines and is over 6MB in size. And, this is not a task that you would want to tackle by hand. I have changed the domains of the hosts that sent the emails to me, but the IP addresses of the attacking hosts have not been modified.