It seems that the other computer was infected with virus lile sasser or Blaster that generate random IP to attack. If you have install firewall, you will be OK.
However, I am highly recommend installing both hardware firewall (like router) and software firewall. It is because the software firewall can block applications request spyware and virus from your computers.
However, I am highly recommend installing both hardware firewall (like router) and software firewall. It is because the software firewall can block applications request spyware and virus from your computers.