电脑和网络已经成了我们生活必不可少的一部分。免费的网络随处可得,它们安全吗? All over the world the need for more laptops and computers increases each year.Networks have been part of our life.Probably everyone with a portable device has once logged on to a public WiFi network without paying for it,while they are having a coffee,on a train,in a shopping mall or at a hotel.However,is this kind of public WiFi network safe?