Newly Observed Hostnames (NOH)¶

The NOH feed offers a more granular view by listing fully qualified domain names (FQDNs) the first time they are observed. This is crucial for detecting threats like phishing and domain shadowing that often use unique subdomains on legitimate-looking domains to evade detection. The NOH feed typically has a much higher volume than the NOD feed, identifying about ninety new hostnames per second.

Overview¶

Hostnames are fully qualified domain names (for example, www.example.com or mail.subdomain.example.com), and the feed emits them as they're observed.

Use this feed when you need to:

Detect phishing attempts that utilize unique subdomains on legitimate-looking domains
Identify domain shadowing tactics where attackers create malicious subdomains on compromised legitimate domains
Enhance real-time threat detection with high-volume hostname data
Monitor subdomain creation patterns for security analysis

Inclusion criteria: Fully qualified domain names (FQDNs) observed in passive DNS for the first time.

Requirements¶

You need the following to access Threat Feeds:

An Enterprise Account with DomainTools, accessible at https://account.domaintools.com/my-account/
Authentication credentials (API key for header authentication, or API username and key for HMAC or open key authentication)
A way to interact with a REST API delivered through AWS CloudFront

Obtain your API credentials from your group's API administrator. API administrators can manage their API keys at https://research.domaintools.com, selecting the drop-down account menu and choosing API admin.

For assistance, contact enterprisesupport@domaintools.com.

Authentication¶

You can authenticate to the NOH APIs using three different methods. Choose the method that best fits your security requirements and technical environment.

API key (header) authentication¶

Authenticate your requests by including the API key in the header of each HTTP request. The API key serves as a unique identifier and authenticates your requests.

Required header:

X-Api-Key: YOUR_API_KEY

Examples:

# Feed API request
curl -H 'X-Api-Key: YOUR_API_KEY' \
  'https://api.domaintools.com/v1/feed/noh/?sessionID=myPhishDetector'

# Download API request
curl -H 'X-Api-Key: YOUR_API_KEY' \
  'https://api.domaintools.com/v1/download/noh/'

HMAC authentication¶

HMAC authentication is a secure alternative to API key-based methods. It requires signing each request with a SHA1 HMAC digest derived from your API secret, providing integrity and authenticity without exposing credentials directly in the request.

This method is recommended for systems where authentication credentials shouldn't be stored in plain text or included directly in request URLs.

DomainTools supports MD5, SHA1, and SHA256 for the hashing algorithm.

Required query parameters:

api_username: Your DomainTools API username
signature: HMAC-SHA1 signature of api_username + timestamp + uri_path
timestamp: Current UTC timestamp in ISO 8601 format (for example, 2025-06-01T15:30:00Z)

Constructing the HMAC signature:

signature = HMAC-SHA1(api_key, api_username + timestamp + uri_path)

URI path must include API version

The uri_path parameter must include the API version prefix. For example, use /v1/feed/nod/ not /feed/nod/.

Example Python signing function:

import hmac
import hashlib

def sign(api_username, api_key, timestamp, uri):
    params = f"{api_username}{timestamp}{uri}"
    return hmac.new(api_key.encode("utf-8"), params.encode("utf-8"), hashlib.sha1).hexdigest()

HMAC timestamp requirements

The timestamp parameter in HMAC authentication must be current (within a few minutes of the server time). The timestamps shown in these examples are static for demonstration purposes. In production, generate a fresh timestamp for each request using your system's current time in ISO 8601 UTC format (e.g., 2025-01-06T15:30:00Z).

Examples:

# Feed API request with HMAC
curl 'https://api.domaintools.com/v1/feed/noh/?api_username=YOUR_USERNAME&signature=HMAC_SIGNATURE&timestamp=2025-01-06T15:30:00Z&sessionID=myPhishDetector'

# Download API request with HMAC
curl 'https://api.domaintools.com/v1/download/noh/?api_username=YOUR_USERNAME&signature=HMAC_SIGNATURE&timestamp=2025-01-06T15:30:00Z'

Open key authentication¶

This is the easiest authentication scheme to implement, but also the least secure. Each request contains the full API key and API username as query parameters. We recommend using API key header authentication or HMAC authentication instead.

If you're unsure about your authentication options, contact enterprisesupport@domaintools.com.

Required query parameters:

api_username: Your API username
api_key: Your API key

Examples:

# Feed API request
curl 'https://api.domaintools.com/v1/feed/noh/?api_username=YOUR_USERNAME&api_key=YOUR_API_KEY&sessionID=myPhishDetector'

# Download API request
curl 'https://api.domaintools.com/v1/download/noh/?api_username=YOUR_USERNAME&api_key=YOUR_API_KEY'

Real-time Feed API¶

The Feed API provides real-time access to current NOH data. Use this API to poll for the latest feed updates at regular intervals, maintain a session to track your position in the feed, and filter results based on your specific needs. Due to the high volume of this feed (~90 hostnames per second), consider using appropriate filtering and polling strategies.

Base URL¶

https://api.domaintools.com/v1/feed/noh/

Rate limits¶

Real-time feeds have the following rate limits:

2 queries per minute
120 queries per hour

If you exceed these limits, the API returns an error.

Response formats¶

The API supports two response formats:

NDJSON (Newline-Delimited JSON)

Default format when no Accept header is specified
Also known as JSON Lines (JSONL)
One JSON object per line
Efficient for streaming and processing large datasets
Set Accept: application/x-ndjson to explicitly request this format

CSV (Comma-Separated Values)

Set Accept: text/csv to request CSV format
Add &headers=1 to the query parameters to include column headers as the first line
Not available for all feeds (for example, the Parsed Domain RDAP feed doesn't support CSV)

Session management¶

Session management allows you to maintain your position in the feed data stream, ensuring you don't miss or duplicate events when polling the API.

How sessions work:

Start a new session: Provide a unique sessionID parameter of your choosing. By default, the API returns the past hour of results.
Resume a session: Use the same sessionID in subsequent requests. The API returns all data since your last request.
Handle large result sets: If a single request exceeds 10M results, the API returns an HTTP 206 response code. Repeat the same request with the same sessionID to receive the next batch of data until you receive an HTTP 200 response code.
Delete a session: Use an HTTP DELETE request with your sessionID to clear the saved offset and start fresh.

Session ID requirements:

1 to 64 characters in length
Alphanumeric characters and hyphens only ([a-zA-Z0-9-]+)
Case-sensitive

Quick start¶

The standard access pattern is to periodically request the most recent feed data, as often as every 60 seconds.

curl -H 'X-Api-Key: YOUR_API_KEY' \
  'https://api.domaintools.com/v1/feed/noh/?sessionID=myPhishDetector'

This starts a new session and returns the last hour of data. Subsequent calls with the same sessionID return data since the last request.

Parameters¶

`sessionID`¶

Type: String

Valid values: 1-64 alphanumeric characters and hyphens ([a-zA-Z0-9-]+)

Description: A unique identifier for the session, used for resuming data retrieval from the last point. Use a new sessionID to begin a new session, fetching the most recent hour by default. Reuse the same sessionID to return all feed data since your last request. If omitted, time window parameters (such as after/before) are required.

Example: sessionID=mySOC

Required: Yes, to continue where you left off (or use after/before instead)

`after`¶

Type: Integer or string

Valid values:

Integer: -1 to -432,000 (relative seconds before current time)
String: ISO 8601 datetime in UTC format (YYYY-MM-DDTHH:MM:SSZ)

Description: The start of the query window (inclusive). When using an integer, the value is in seconds relative to the current time. When using a string, provide an absolute timestamp. The timestamp must represent a point between 1 second ago and 5 days ago, relative to the current UTC time.

Example: after=-60 or after=2024-10-16T10:20:00Z

Required: Yes, if before or sessionID not provided

`before`¶

Type: Integer or string

Valid values:

Integer: -1 to -432,000 (relative seconds before current time)
String: ISO 8601 datetime in UTC format (YYYY-MM-DDTHH:MM:SSZ)

Description: The end of the query window (inclusive). When using an integer, the value is in seconds relative to the current time. When using a string, provide an absolute timestamp. The timestamp must represent a point between 1 second ago and 5 days ago, relative to the current UTC time.

Example: before=-120 or before=2024-10-16T10:20:00Z

Required: Yes, if after or sessionID not provided

`domain`¶

Type: String

Valid values: Domain character set restricted by the DNS specification (letters, digits, hyphens). International characters should be specified in punycode. A trailing dot is acceptable.

Description: Filter for an exact domain or a domain substring by prefixing or suffixing your string with *. Multiple parameters are supported (for example, ?domain=*apple*&domain=*microsoft*). The URL-encoded version of * (%2A) may be required in some clients.

Example: domain=*bank* or domain=example.com

Required: No

`fromBeginning`¶

Type: Boolean

Valid values: true

Description: Functions with new session IDs to return the first hour (rather than the last). Returns an error if the session ID already exists. Only the value true is accepted; any other value (including false) will be ignored or treated as omitted.

Example: fromBeginning=true

Required: No

`top`¶

Type: Integer

Valid values: Positive integer, 1-1,000,000,000

Description: Limits the number of results in the response payload. Primarily intended for testing. When you apply this parameter to risk feeds, results are sorted by overall_risk (descending).

Example: top=10

Required: No

`headers`¶

Type: Integer

Valid values: 1

Description: Adds a header row as the first line of the response when text/csv is requested. Set headers=1 to enable. Only applies when requesting CSV format. Only the value 1 is accepted; any other value is invalid.

Example: headers=1

Required: No

Response structure¶

The API returns responses in NDJSON (Newline-Delimited JSON), with each response containing one domain entry per line. Each entry contains a timestamp in ISO 8601 UTC format, and the domain.

Response fields:

timestamp (string): The observation timestamp in ISO 8601 UTC format.

Example: "timestamp":"2024-11-15T16:14:39Z"

domain (string): The domain name without the trailing dot. Domain character set restricted by the DNS specification (letters, digits, hyphens).

Example: "domain":"example.com"

Example NDJSON response:

{"timestamp":"2024-11-15T16:14:39Z","domain":"domiantools.com"}
{"timestamp":"2024-11-15T16:14:38Z","domain":"domsintools.com"}
{"timestamp":"2024-11-15T16:14:36Z","domain":"edomaintools.com"}
{"timestamp":"2024-11-15T16:14:35Z","domain":"omaintools.com"}
{"timestamp":"2024-11-15T16:14:35Z","domain":"v-domaintools.com"}

Example CSV response:

timestamp,domain
2024-11-15T16:14:39Z,domiantools.com
2024-11-15T16:14:38Z,domsintools.com
2024-11-15T16:14:36Z,edomaintools.com

Response codes¶

Code	Status	Description
`200`	OK	The request was successful and all data has been delivered
`206`	Partial content	The request was successful, but only a portion of the data was returned. The request exceeded 10M results or the 1-hour evaluation window. Repeat the same request with the same `sessionID` to receive the next batch of data until you receive an HTTP `200` response
`400`	Bad request	The request is malformed
`403`	Forbidden	Missing or invalid API credentials
`404`	Not found	The requested resource (such as a `sessionID`) doesn't exist
`406`	Not acceptable	The specified `Accept` header value isn't supported. Only `application/x-ndjson` and `text/csv` are accepted
`422`	Unprocessable entity	The request is syntactically valid but violates semantic or domain-specific rules (for example, invalid query parameter values)

Examples¶

Basic session polling:

# Start a new session
curl -H 'X-Api-Key: YOUR_API_KEY' \
  'https://api.domaintools.com/v1/feed/noh/?sessionID=myPhishDetector'

# Resume the session (returns data since last request)
curl -H 'X-Api-Key: YOUR_API_KEY' \
  'https://api.domaintools.com/v1/feed/noh/?sessionID=myPhishDetector'

Time window filtering:

# Get data from a specific time range
curl -H 'X-Api-Key: YOUR_API_KEY' \
  'https://api.domaintools.com/v1/feed/noh/?after=2025-01-06T10:00:00Z&before=2025-01-06T11:00:00Z'

Domain filtering:

# Filter for specific hostname patterns (useful for monitoring specific domains)
curl -H 'X-Api-Key: YOUR_API_KEY' \
  'https://api.domaintools.com/v1/feed/noh/?domain=*.example.com&sessionID=myPhishDetector'

CSV format:

# Request CSV format with headers
curl -H 'Accept: text/csv' -H 'X-Api-Key: YOUR_API_KEY' \
  'https://api.domaintools.com/v1/feed/noh/?headers=1&sessionID=myPhishDetector'

# Request CSV format without headers
curl -H 'Accept: text/csv' -H 'X-Api-Key: YOUR_API_KEY' \
  'https://api.domaintools.com/v1/feed/noh/?sessionID=myPhishDetector'

Handling large result sets:

# If you receive HTTP 206, repeat the request to get the next batch
curl -H 'X-Api-Key: YOUR_API_KEY' \
  'https://api.domaintools.com/v1/feed/noh/?sessionID=myPhishDetector'

# Repeat until you receive HTTP 200
curl -H 'X-Api-Key: YOUR_API_KEY' \
  'https://api.domaintools.com/v1/feed/noh/?sessionID=myPhishDetector'

Delete a session:

# Clear the saved offset and start fresh
curl -X DELETE -H 'X-Api-Key: YOUR_API_KEY' \
  'https://api.domaintools.com/v1/feed/noh/?sessionID=myPhishDetector'

Download API¶

The Download API provides access to historical NOH data through temporary AWS S3 file links. Use this API to retrieve archived data you may have missed or to backfill your systems with historical information. Files are organized by hour and available for 90 days.

Base URL¶

https://api.domaintools.com/v1/download/noh/

Parameters¶

`limit`¶

Type: Integer

Valid values: Positive integer

Description: Limits the number of files returned in the response, starting from the most recent. Use to control payload size or test specific cases.

Example: limit=10

Required: No

Response structure¶

The API returns a JSON response containing an array of downloadable files. Each file entry includes:

download_name (string): The feed identifier (noh)

files (array): List of downloadable file entries

Each file object contains:

name (string): Path and filename of the downloadable file
last_modified (string): Timestamp of last modification in ISO 8601 UTC format
etag (string): ETag (hash) used to verify file identity and versioning
size (integer): File size in bytes
url (string): Temporary signed URL to download the file from AWS CloudFront

File naming convention:

Data file: noh/{YYYY-MM-DD}/noh-{YYYYMMDD}.{HH00}-{HH00}.json.gz
Checksum file: noh/{YYYY-MM-DD}/noh-{YYYYMMDD}.{HH00}-{HH00}.json.gz.sha256

Example response:

{
  "response": {
    "download_name": "noh",
    "files": [
      {
        "name": "noh/2024-11-19/noh-20241119.1900-2000.json.gz.sha256",
        "last_modified": "2024-11-19T20:00:11+00:00",
        "etag": "\"67a6d9b0973b2d31ffb779dc8f7f8cfa\"",
        "size": 64,
        "url": "https://download.example.com/noh/2024-11-19/noh-20241119.1900-2000.json.gz.sha256?Expires=..."
      },
      {
        "name": "noh/2024-11-19/noh-20241119.1900-2000.json.gz",
        "last_modified": "2024-11-19T20:00:11+00:00",
        "etag": "\"67a6d9b0973b2d31ffb779dc8f7f8cfa\"",
        "size": 324850,
        "url": "https://download.example.com/noh/2024-11-19/noh-20241119.1900-2000.json.gz?Expires=..."
      }
    ]
  }
}

Response codes¶

Code	Status	Description
`200`	OK	The request was successful
`400`	Bad request	The request is malformed
`403`	Forbidden	Missing or invalid API credentials
`422`	Unprocessable entity	The request is syntactically valid but violates semantic or domain-specific rules (for example, invalid query parameter values)

File contents¶

The *.json.gz.sha256 file is a checksum containing a SHA-256 hash value used to verify the integrity of the downloaded file.

The *.json.gz file, when uncompressed, contains JSON data in the same format as the Feed API response (NDJSON with timestamp and domain fields, where domain contains the full hostname).

Examples¶

List available files:

# Get the most recent files
curl -H 'X-Api-Key: YOUR_API_KEY' \
  'https://api.domaintools.com/v1/download/noh/?limit=10'

Download and verify a file:

# Get the file list
curl -H 'X-Api-Key: YOUR_API_KEY' \
  'https://api.domaintools.com/v1/download/noh/?limit=2' > files.json

# Extract the URL and download the data file
curl -o noh-data.json.gz "$(jq -r '.response.files[1].url' files.json)"

# Download the checksum file
curl -o noh-data.json.gz.sha256 "$(jq -r '.response.files[0].url' files.json)"

# Verify the integrity
sha256sum -c noh-data.json.gz.sha256

Batch processing:

# Download multiple files in a loop
for url in $(curl -H 'X-Api-Key: YOUR_API_KEY' \
  'https://api.domaintools.com/v1/download/noh/?limit=24' | \
  jq -r '.response.files[].url' | grep '\.json\.gz$'); do
  curl -O "$url"
done

Newly Observed Hostnames (NOH)¶

Overview¶

Requirements¶

Authentication¶

API key (header) authentication¶

HMAC authentication¶

Open key authentication¶

Real-time Feed API¶

Base URL¶

Rate limits¶

Response formats¶

Session management¶

Quick start¶

Parameters¶

sessionID¶

after¶

before¶

domain¶

fromBeginning¶

top¶

headers¶

Response structure¶

Response codes¶

Examples¶

Download API¶

Base URL¶

Parameters¶

limit¶

Response structure¶

Response codes¶

File contents¶

Examples¶

Related resources¶

`sessionID`¶

`after`¶

`before`¶

`domain`¶

`fromBeginning`¶

`top`¶

`headers`¶

`limit`¶