Free tools are restricted to home or personal use, but a few are also available for businesses. Comodo Internet Security (CIS) provides a sturdy package for blocking viruses, spyware, rootkits, botnets, worms, and other malware. Microsoft Security Essentials protects Windows systems against viruses and spyware. The Firewall and Defense+ features are highly customizable, too. You can fine-tune the protection by using rules, policies, definitions of trusted files/networks.”]
Source: https://www.csoonline.com/article/2129519/free-internet-security-for-small-businesses.html