The document discusses computer viruses including their definition, types, symptoms, methods of infection, and prevention techniques. A computer virus is a malicious program that can self-replicate and spread between computers without the owner's permission. Common types include worms, Trojan horses, and botnets. Signs of infection include computers not booting, slow performance, and random crashing. Viruses primarily spread through email attachments, rogue websites, and infected removable drives. Regular scanning and software/OS updates can help prevent virus infections.