The document discusses computer viruses and antivirus software. It defines computer viruses as malicious software that can infiltrate or damage systems without consent. It notes that viruses need a host program to spread, while worms do not. The document recommends using antivirus software and taking computers to experts to keep systems safe from viruses. It provides criteria for choosing antivirus software, including detection abilities, interface, memory usage, and price. BKAV, a free antivirus software developed in Vietnam, is recommended as a suitable low-cost option.