This document provides an overview of computer viruses. It discusses how viruses spread by attaching themselves to files and transferring between computers. Various types of viruses are described like boot viruses, polymorphic viruses, macro viruses, worms, and trojans. Symptoms of a virus infection include slow performance, reduced memory, and files becoming corrupted. The document recommends installing antivirus software, regularly updating it, and being cautious of email attachments to prevent and cure virus infections.