As the CISO of a publicly traded company, I would implement virus protection, backup sites, and physical security precautions to ensure availability for my systems. Therefore, guaranteeing access to clients whenever it is needed.
Virus protection is essential in order to prevent malware or other viruses from preventing system or network availability. Having a reliable virus protection service that is updated on time will alarm systems if a know virus is being installed onto a system.
If virus protection fails and a system or network failure occurs, backup sites are the best possible last resort. Although backup sites are expensive and require a lot of work to maintain, backup sites allow you to keep systems available while the original systems are being fixed. With backup sites, the second your systems go down, the backup site takes over with the last working backup of your original system.
One of the most basic but most important protections necessary is physical security. Machines and servers must be kept in a safe environment with doors that are locked when the site is unattended. Security cameras are also necessary for deterring braking and entering and for catching those who may have attempted to break in. These implementations of physical security will help to ensure that machines and networks will not be physically tampered with, thus ensuring their availability.