The document discusses different types of computer viruses and malicious programs such as worms and Trojan horses. It describes how viruses can spread through email attachments, shared files, floppy disks, and infected documents. The document provides tips for preventing viruses, such as installing and updating antivirus software, avoiding unexpected email attachments, and keeping operating systems and programs up to date. It also outlines signs that a computer may have a virus and explains what to do if a virus is suspected.