As a matter of fact, the USB flash drive is the very breeding ground for most viruses/trojans today. They (including the famous WannaCry ransomware attack) initially infect portable storage devices, then spread across the entire LAN, and finally seize any networking opportunity to spread themselves to the Internet. On the other hand, they usually move from the USB device to some key nodes of LANs, which leads to the network paralysis and Internet disaster in the end.