# Domain Discovery

Domain discovery allows you to add domains you know about (for instance, `example.com`) and let us find subdomains and alternate TLDs (such as `example.net`).

## Detection Methods

We use several methods to discover hostnames:

1. **Guessing**

   We use a large database of potential subdomains and check whether they exist. This is also referred to as a *brute force* method. The checks are fast and lightweight to not overwhelm your DNS servers.
2. **Databases & Public Information**

   We use a variety of databases, certificate transparency logs, and other sources that contain subdomain records.
3. **Third-party Integrations**

   We can easily integrate with your DNS servers like Amazon Route53, Azure, and Cloudflare to pull subdomains from your DNS records, or provide instructions for exporting a list from your DNS provider.

{% hint style="info" %}
This process is run recursively, so if we discover<mark style="background-color:yellow;">`sub.example.com`</mark> we'll use that to discover deeper subdomains, such as <mark style="background-color:yellow;">`third.sub.example.com`</mark>.
{% endhint %}

## Seed Domains

We call the domains you add to discovery *seed domains* and you can add those from your dashboard or by sending a list or CSV to our team. By default, we use the domain on your email address to seed your account initially.

### Add Seed Domains

You can add new seed domains at any time on *Discovery* → *Domain* → [Add](https://app.halosecurity.com/user/settings/seeds/domains/add). You'll see a list of suggested domains that are not currently included in your domain discovery.

### Remove Seed Domains

You can remove domains from discovery by clicking the ✕ icon next to a domain on \_Discovery → \_ [Domain](https://app.halosecurity.com/user/settings/seeds/domains/).

## Discovery Process

Each week we'll run our discovery process and compile discovered subdomains. You can also run the discovery process on demand by visiting *Settings* → *Seeds* → [Domain](https://app.halosecurity.com/user/settings/seeds/domains/) and clicking the refresh icon in the row of the domain you'd like to run the process on.

## Discovered Subdomains

All hosts found during the domain discovery process are reflected in the [Assets](https://app.halosecurity.com/user/security/discovery/list) report. You can filter discovered targets in the source dropdown to see only ones discovered with domain discovery, or from a specific domain.

For more details on managing discovered domains, see [Discovered Assets](/docs/platform/discovery/discovered-assets.md).


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