Wildcard DNS Record: Setup, Benefits, and Security

A wildcard DNS record is a type of DNS record that allows you to map a domain to all its subdomains with a single record. This is done by using a special syntax, such as *.example.com, which matches any subdomain of example.com.

Wildcard DNS records are useful for managing multiple subdomains, as they eliminate the need for creating separate DNS records for each subdomain. This can be especially helpful for large websites or applications with many subdomains.

The benefits of using wildcard DNS records include improved efficiency and reduced administrative overhead. By having a single record that covers all subdomains, you can simplify your DNS management and reduce the risk of errors.

Wildcard DNS records can be set up using various DNS providers, and the process typically involves creating a new DNS record with the wildcard syntax and specifying the domain name.

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Creating a Wildcard DNS record is a straightforward process. You can create a wildcard DNS record by adding an * in the Name field of a DNS record.

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To start managing Wildcard DNS records for your domain name, you'll need to create a new DNS zone and add the Wildcard DNS records you need. This can be done by logging in to your control panel and following the steps outlined in Example 3.

You can create a wildcard DNS record specifically for a deeper subdomain by adding the subdomain name before the * in the Name field. For example, to create a wildcard record on *.www.example.com, you would create a record with *.www in the name field.

Wildcard DNS records can be added for various record types, including A, AAAA, MX, TXT, CNAME, ALIAS, and WR. The TTL for Wildcard DNS records is typically set to 1 hour.

Here are the basic requirements for creating a Wildcard DNS record:

Note that a Wildcard Record can be added only for A (or AAAA), MX, TXT, CNAME, ALIAS, or Web Redirect record types.

Wildcard DNS records simplify subdomain management by directing all unspecified subdomains to a single destination, reducing the need to create individual DNS records for each subdomain.

This makes management more efficient, especially in environments where new subdomains are added regularly. Wildcard records automatically handle DNS resolution, making it easier to scale up without constant manual adjustments.

Wildcard records allow for the creation of default pages or content for unconfigured subdomains, ensuring a consistent user experience throughout the domain and improving brand consistency.

Here are the main benefits of implementing wildcard DNS records:

Wildcard records are particularly useful in dynamic or large-scale environments, where new subdomains are frequently added. By using a wildcard DNS entry, any subdomain, whether it currently exists or not, will resolve as valid.

To create a Wildcard DNS record, you'll need to create a DNS record with an * in the Name field. This can be done for various record types, including A, AAAA, MX, TXT, CNAME, ALIAS, or WR.

You can also create a wildcard DNS record specifically for a deeper subdomain, such as *.www.example.com. To do this, create a record with *.www in the name field.

Wildcard DNS records can be added for A (or AAAA), MX, TXT, CNAME, ALIAS, or Web Redirect record types. The TTL (Time To Live) should be set to 1 Hour, and the Host should be set to *.

To check if a wildcard DNS record is correctly configured for a domain, you can use the Nslookup or Dig command. For Windows users, open the Command Prompt and use the Nslookup command followed by a random subdomain. For Linux/macOS users, open the Terminal and use the Dig command followed by a random subdomain.

Here's a list of common record types that support wildcard DNS records:

Note that wildcard DNS setups may vary, and testing with various non-existent subdomains can provide more comprehensive insights.

Wildcard DNS records can function as a double-edged sword, providing a layer of security by hiding real subdomains but also hindering defensive security tools.

This obscurity can slow down attackers, as they struggle to identify which subdomains are valid targets. Wildcard domains can make discovery more difficult, reducing the quality of OSINT sources and complicating efforts to detect expired or unused domains.

The Outpost24 EASM platform faced this challenge with wildcard domains, struggling to distinguish configured subdomains from false positives.

Wildcard DNS records can provide a layer of security by hiding real subdomains within a sea of possible names, making it harder for attackers to identify valid targets. This is known as "Security Through Obscurity".

However, this obscurity can also hinder defensive security tools, making it difficult to detect expired or unused domains, or identify new threats. This is because every domain seems active, reducing the quality of OSINT (Open Source Intelligence) sources.

Wildcards can function as a barrier to security, complicating efforts to distinguish configured subdomains that are truly part of an organization's external attack surface from false positives. This is a challenge faced by the Outpost24 EASM platform, which requires constant improvement and adjustment of search techniques and methods.

The main limitation of wildcard DNS records is that specific DNS records take precedence over wildcard records. This means that a specific record on any equal or lower level will terminate anything on or below this specific record.

Here's a summary of the order of precedence:

For example, if you have a wildcard record for *.example.com and a specific record for subdomain1.example.com, the specific record will take precedence for subdomain1.example.com and anything below it.

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Identifying domains in your attack surface is crucial for maintaining online security. Accurately identifying wildcard domains is a difficult challenge in External Attack Surface Management.

Our approach to identifying wildcard domains involves advanced detection logic and AI-powered domain discovery. This ensures that only true, vulnerable subdomains are flagged.

Wildcard domains can be a blind spot in External Attack Surface Management. At Outpost24, we've spent years refining our approach to make sure wildcard domains are no longer a blind spot.

Our EASM platform uses continuous monitoring to separate real, exposed assets from misleading wildcard responses. This leads to a complete and accurate view of your organization's online exposure.

Wildcard DNS records are a powerful tool for simplifying DNS management, but they can be tricky to understand. A wildcard DNS record in a zone file looks similar to this example: *.example.com.

The wildcard DNS record will cause DNS lookups on domain names ending in example.com that do not exist to have MX records synthesized for them. So, a lookup for the MX record for somerandomname.example.com would return an MX record pointing to host1.example.com.

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The original definition of how a DNS wildcard behaves is specified in RFC1034 sections 4.3.2 and 4.3.3, but only indirectly by certain steps in a search algorithm. This can result in the rules being neither intuitive nor clearly specified.

A wildcard DNS record will not match cases where there are no matching records of the type that has been queried for. This means that if there is a wildcard MX for *.example.com, and an A record (but no MX record) for www.example.com, the correct response to an MX request for www.example.com is "no error, but no data".

The following responses would not be synthesized from any of the wildcards in the zone: requests for subdomains that have existing DNS records, such as A records or other types of records.

A wildcard domain is a domain name that uses a wildcard character (usually an asterisk “*”) to represent one or more subdomains. This allows all subdomains of a given domain to be matched and handled by a single DNS record or SSL certificate.

Here are some key characteristics of wildcard DNS records:

A wildcard domain responds to requests for any subdomain under a specified domain, typically configured using a leading dot, such as .domain.com or .sub.domain.com. This setup ensures that any subdomain request — no matter what precedes the domain — will be handled correctly, as if the subdomain exists.

ClouDNS offers full support for Wildcard DNS records for all its DNS services, including Free DNS, Premium DNS, DDoS Protected DNS, and GeoDNS.

You can get assistance with your Wildcard records configuration by contacting their Technical Support team, which is available 24/7 via live chat and tickets.

Here are some ClouDNS services that support Wildcard DNS records:

Customers on all plans can create and proxy wildcard DNS records, making it a convenient option for those who need it.

Wildcard DNS record support is a game-changer for many users. Customers on all plans can create and proxy wildcard DNS records.

ClouDNS provides full support for Wildcard DNS records for all their DNS services, including Free DNS, Premium DNS, DDoS Protected DNS, and GeoDNS.

If you need assistance with your Wildcard records configuration, you can reach out to their technical support team, who are available 24/7 via live chat and tickets.

Here are the specific DNS services that support Wildcard records:

New gTLDs are prohibited from publishing wildcards by specification 6 of the ICANN New gTLD Base Registry agreement.

However, ICANN's Name Collision Occurrence Management Framework requires new gTLDs to publish special records for at least 90 days. These records include MX, SRV, TXT, and 127.0.53.53 A record wildcards that warn of potential name collisions.

New gTLDs must publish these special records to mitigate the risk of name collisions due to relative domain names with domain search paths.

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Wildcard domains are widely used by blogging websites that allow users to create sub-domains upon demand, such as WordPress or Blogspot.

Free Dynamic DNS websites also use wildcard domains to allow users to create a DNS name that changes to match their host IP as the IP address is changed periodically by their ISP's DHCP server.

Several domain name registrars have deployed wildcard records for the top-level domains to provide a platform for advertising, most notably VeriSign for .com and .net.

As of March 2018, top-level domains using a wildcard A record are .fm, .la, .ph, .pw, .vg, and .ws, and also the internationalized TLDs .中国 and .გე.

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Wildcard DNS records are widely used by blogging websites that allow users to create sub-domains upon demand.

For example, sites like WordPress and Blogspot use wildcard domains to enable users to create their own sub-domains.

Another popular use of wildcard DNS records is by Free Dynamic DNS websites that allow users to create a DNS name that changes to match their host IP as the IP address is changed periodically by their ISP's DHCP server.

These types of websites are particularly useful for users who frequently change their internet service provider or have a dynamic IP address.

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Some top-level domains, like .fm, .la, .ph, .pw, and .ws, currently use wildcard A records.

VeriSign once used wildcard records for .com and .net with its Site Finder system, but it has since been removed.

The .museum TLD had a wildcard record, which has also been removed.

As of March 2018, only .fm, .la, .ph, .pw, .vg, and .ws, along with internationalized TLDs .中国 and .გე, use wildcard A records.

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The *.中国 wildcard resolves to ibaidu.com, which has been flagged as unsafe by Chrome.

ISPs often synthesize address records for typos, a practice called "catchall" typosquatting.

However, these synthesized records aren't true wildcards, but rather modified caching name servers.

Some developers have created software patches to filter out wildcard DNS records from specific domains.

For example, the Internet Software Consortium produced a version of the BIND DNS software that can be configured to ignore wildcard DNS records.

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