Initially the software will have been emailed to a user, once they open it it can use the worm effect to infect all other machines on a network. It takes one pe

Initially the software will have been emailed to a user, once they open it it can use the worm effect to infect all other machines on a network. It takes one person to open the software, however it seems that they sent it to lots of addresses and so you only need one weak point(person) on a network and voila it can spread itself.