An organization is developing a new web-based application to process orders from customers. Which of the following security measures should be taken to protect this application from hackers?

A. Ensure that ports 80 and 443 are blocked at the firewall.
B. Inspect file and access permissions on all servers to ensure that all files have read-only access.
C. Perform a web application security review.
D. Make sure that only the IP addresses of existing customers are allowed through the firewall.