Wildcard Domain

Requests for nonexistent domains and subdomains are handled via wildcard DNS domains. Instead of producing a separate resource record for each domain, wildcard domains are used to redirect inquiries for all nonexistent domains or subdomains to a single server. A wildcard DNS domain is most commonly used to construct a zone that forwards mail from the internet to another mail system. The leftmost label of a domain name in a wildcard domain is an asterisk (*).

Why do users use a wildcard record?

A wildcard DNS record is a type of record that responds to DNS requests for subdomains that have not yet been declared by users. In other words, using wildcard records like (*.example.com), it doesn't matter if people reach the website through (ww.example.com) or (www.example.com). A wildcard domain is especially handy if users want subdomains to display whatever the document root is set to. Most wildcards are usually set to the site's homepage as a preference. Wildcard domains are especially beneficial for multiuser web applications that necessitate the usage of a wildcard subdomain and minimize propagation delays. The wildcard domain is configured directly in DNS with no document root when using it to reduce propagation delays. Any new subdomains will be resolved shortly after that.

Why is using wildcard certificates risky?

A wildcard certificate is a public key certificate that is shared across all subdomains of a bigger domain. Users can instantly secure infinite subdomains that are all encrypted by the same certificate by using a wildcard certificate on a publicly visible web server. Unfortunately, cybercriminals can do the same. Wildcard certificates can be used in a variety of ways by cybercriminals:

A web server that has been hacked: When users utilize a wildcard certificate on public-facing web servers, cybercriminals may be more likely to use that webserver to host malicious sites for phishing campaigns.

Stolen Private key. If cyber criminals obtain access to the private key of a wildcard certificate, they may be able to impersonate any domain that is covered by that certificate.

Certificate forgery. Cybercriminals can utilize wildcard certificates to construct subdomains and set up phishing sites if they mislead a certificate authority into issuing a wildcard certificate for a fictional firm.