If you download software from not trusted websites. Inserting USB drive to infected computer transfer the virus to healthy computer, viruses make copy of itself that infect all your files.
Contact Us:
Norton.com/setup Antivirus
Address: 30 WINNEPOGE DR. FAIRFIELD CT 06825
Phone: +1-844-882-8639
Visit Us: http://www.nortoncom-setup.com/norton-product-key/