Which action would most effectively increase the security of a virtual-hosted web server?

According to CEH v13 Web Application and Server Security, regular patching and updates are the most effective way to reduce server attack surfaces. Vulnerabilities in web servers, proxies, and supporting services are frequently exploited if patches are delayed.

While architectural choices and directory placement influence organization, they do not mitigate known vulnerabilities. Changing IP addresses does not prevent exploitation, and moving directories does not address underlying software flaws.

CEH v13 consistently emphasizes patch management as a primary defensive control. Therefore, Option C is correct.