This document discusses antivirus software, types of free antivirus programs, firewalls, and types of viruses that can be received in emails. It describes how antivirus software aims to detect and eliminate computer viruses. It lists several popular free antivirus programs and explains what a firewall is and how it acts as a barrier between a device and network. It also defines three types of viruses that can be received in emails: Trojan horses, worms, and macro viruses.