What allows a certificate to secure multiple subdomains by containing an asterisk character in its domain name field?

A certificate that includes an asterisk character in its domain name field is known as a Wildcard certificate. This type of certificate is specifically designed to secure multiple subdomains under a single domain, which significantly simplifies the management of SSL/TLS certificates for organizations that operate numerous subdomains.

For example, a Wildcard certificate issued for "*.example.com" can secure subdomains such as "blog.example.com," "mail.example.com," or "shop.example.com," all with one certificate. This not only reduces costs related to purchasing multiple certificates but also streamlines deployment and renewal processes.

In contrast, Extended Validation (EV) and Domain Validation (DV) certificates relate more to the validation processes and levels of trust associated with issuing certificates rather than their functionality in securing multiple subdomains. General purpose does not specifically refer to the capability of securing multiple subdomains with a wildcard character, but rather could imply certificates that serve a broad range of uses without focusing on the wildcard functionality. Thus, the correct choice is indeed the Wildcard certificate, as it is specifically tailored for securing various subdomains under a single primary domain.