If I were a CISO for a publically traded company, I would implement various protections to ensure that my systems were available and secure. Here are some of the measures I would do.

Backups
Frequent backups are necessary to prevent data loss. I would make sure these backups are either separate from the main system or offline.

DDOS prevention software
Software such as CAPTCHA (Completely Automated Public Turning Test To Tell Computers and Humans Apart) and/or the “I am not a robot” checkbox are a key aspect of preventing DDOS attacks.

AntiVirus/AntiMalware
The most basic form of data security is antivirus/antimalware. I would make sure that this was installed on all my systems.

Physical Security
Physical security is important, but commonly overlooked, part of data security and availability. If I were the CISO, I would make sure the data systems are protected by cameras, locked doors, and security guards.

Phishing/Bowser Attack Prevention
I would make sure my company properly trains employees to recognize and report fake emails and websites pretending to be from the company. These types of scams can give hackers access to the company’s system. I also would require Two Factor Authentication (2FA) for all employees to make sure that if their logins are compromised hackers aren’t able to log in.