There are two types of antivirus software: signature-based and heuristic-based. Signature-based antivirus software uses a list of known malware signatures to detect and remove infections. Heuristic-based antivirus software uses algorithms to detect malware based on its behavior. Both types of antivirus software are available in free and paid versions. Organizations should install antivirus software on all of their computers and keep it up to date to protect themselves from malware infections.