This article is introduces about the possible harm for company and it stand for by the attack tree diagram. In the company have six computer and inside server. Each computer is using Microsoft window 7. They are employing the Disc to store the back up and the router is default setting up. Each employee has the email address. Firstly, I will strike the workstation, try to obtain the password illegally and strike the security such as install pathogen, Trojan, worm and DOS harm. After that, I will attack the movie to receive the dvd and do some harmful action. Obtain the DVD can through the staff, such as bribe or threaten. Destructive action will install the threats into the DVD and propagate to other computer when they are employing the backup.