Antivirus is a type of software that protects a computer or device from malicious software or malware, such as viruses, worms, trojans, spyware, ransomware, etc. Antivirus software requires the most frequent updating to remain effective because new malware threats are constantly emerging and evolving. Antivirus software needs to update its database of malware signatures or definitions, which are the patterns or characteristics that identify known malware. Antivirus software also needs to update its scanning engine or algorithm, which is the method or technique that detects and removes malware. Host firewall, web browser, and device drivers are not types of software that require the most frequent updating to remain effective. Host firewall is a type of software that monitors and controls the network traffic to or from a computer or device based on rules or policies. Web browser is a type of software that allows users to access and view web pages or web applications on the Internet. Device drivers are types of software that enable the communication and interaction between the operating system and the hardware devices. References: CompTIA IT Fundamentals+ Study Guide: Exam FC0-U61, Second Edition, Chapter 8: Security Concepts, page 305.