Integrating through Segment

This guide is also available from Segment's documentation.


Once you enable the Castle integration, the Castle JavaScript snippet will be placed on your website, and you will see user data start appearing in the Castle dashboard.

Client-side tracking will work out of the box, whereas your existing server-side calls will need to be extended with data from the incoming request.

Castle has support for calling identify, page, screen, and group. The alias call is not supported.

Integration steps

  1. Track successful and failed logins
  2. Extend server-side tracking with request properties
  3. identify, preferably on the server-side
  4. Optional: Use Castle's authenticate API to request a risk score
  5. Recommended: Secure Mode

Tracking successful and failed logins

A baseline integration of Castle includes tracking successful and failed login attempts. If you are already tracking these events through your Segment integration, you can use Event Mapping to indicate which of your events that correspond to Castle reserved events.

: If you are going to request a Castle risk score for the "Logged in" event, you should not map that event to Castle's reserved $login.succeeded. Instead, you should authenticate that event through Castle. See next section on Requesting a risk score.

Here are two Ruby examples on how to track successful and failed login attempts (context and integration have been omitted for brevity):

  user_id: '019mr8mf4r',
  event: 'Logged in'

Tracking failed logins enables protection for account threats such as password guessing. If you don't know which user that generated the failed login, simply omit user_id. Instead, whenever you have access to the user-submitted email field, add this to the event properties as email or username depending on how you identify your users. It's OK to send both user_id and email at the same time.

# known user
  user_id: '019mr8mf4r',
  event: 'Failed to log in'

# unknown user
  anonymous_id: UUID.generate,
  event: 'Failed to log in',
  properties: {
    email: ''

: Segment requires either user_id or anonymous_id for the request to be processed. If you don't know which user generated the failed login create a UUID and provide it as anonymous_id

Extending server-side tracking with request properties

Tracking events from your server-side is crucial to prevent requests from getting blocked by malicious actors. This is recommended for all Castle's reserved events, such as logins and password changes.

Server-side track events will get dropped by Castle unless they contain the below properties. identify calls will still create or update a user, but will not create a device if these properties are missing:

  • context.ip. The user's IP address, i.e. not your server's internal IP
  • context.user_agent, alternatively context.headers containing at least the user_agent field.
  • context.client_id. The Client ID forwarded by the web or mobile SDK.

These properties are described more in detail in the next section.

Here’s a Ruby example of a server-side track call extended with request properties:

  user_id: '019mr8mf4r',
  event: 'Logged in'
  context: {
    ip: '',
    user_agent: 'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_9_5) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/40.0.2214.115 Safari/537.36',
    client_id: '7a31b5a1-7e01-4377-b086-5a488ec8a0ca',
    headers: {
      accept_language: 'da, en-gb;q=0.8, en;q=0.7',

If you're concerned about sending client_id and headers to all of your active Segment integrations, instead include them in the integrations.Castle object to keep them private to your Castle integration.

The client_id property

By forwarding a client identifier from the client-side to the server-side, activity from the two sources can be linked together to form a strong protection against attacks where this link is not present.

The Castle JavaScript SDK (loaded by Analytics.js) will forward the client identifier as a browser cookie named __cid.

The Castle iOS and Android SDKs will forward it as the HTTP header X-Castle-Client-Id. See the respective documentation pages for instructions on how to configure the header forwarding.

Here’s a Ruby example on how to extract the Client ID on your server-side:

client_id =
  request.cookies['__cid'] ||

On iOS, forward the device UUID as client identifier:

[request setValue:uuid forHTTPHeaderField:@"X-Castle-Client-Id"];

NSURL *url = [NSURL URLWithString:@""];
NSMutableURLRequest *request = [[NSMutableURLRequest alloc] initWithURL:url];

NSString *uuid = [UIDevice currentDevice].identifierForVendor.UUIDString;

On Android, forward the device identifier from Segment's Utils package as client identifier:

String uuid = Utils.getDeviceId();

OkHttpClient client = new OkHttpClient();
Request request = new Request.Builder()
  .header("X-Castle-Client-Id", uuid)

: If you have a client-less integration, for instance if you're using Castle to protect a customer-facing API, set client_id to false.

The headers property

By forwarding HTTP request headers from the server-side, Castle is able to build a richer device fingerprint and prevent malicious actors from spoofing the client environment.

For privacy reasons, you do not want to send the "Cookie" header to Castle, so make sure you delete if from the list of headers.

  user_agent: 'Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US; rv: Gecko/20091102 Firefox/3.5.5 (.NET CLR 3.5.30729)',
  accept: 'text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8',
  accept_language: 'en-us,en;q=0.5',
  accept_encoding: 'gzip,deflate',
  accept_charset: 'ISO-8859-1,utf-8;q=0.7,*;q=0.7'

There are example implementations on how to extract request headers in PHP, Ruby, and Java.


When you call identify, a user will be created in Castle. The Segment special traits email, username, name, createdAt, phone, and address are mapped to Castle's reserved user traits.

Any additional traits will be stored on the Castle user model as custom traits.

Prevent identify from getting blocked in the client during an account takeover by calling identify from your server.

Here's a complete JavaScript example of an identify call:

analytics.identify('1234', {
  email: '', // recommended
  createdAt: '2015-02-23T22:28:55.387Z', // recommended
  name: 'Johan Brissmyr', // for display
  username: 'brissmyr', // for display
  balance: 1350, // custom trait
  phone: '+1 415 254 9225', // improved risk scoring
  address: { // improved risk scoring
    street: '60 Rausch St',
    city: 'San Francisco',
    state: 'CA',
    postalCode: '94103',
    country: 'USA'

If you're calling authenticate to obtain a risk score, you do not need to call identify from the server-side. Instead, authenticate provides a way to attach traits in the same call.

Secure Mode

Enable Secure Mode to prevent fraudsters from impersonating your users.

Secure Mode is highly encouraged for production deployments, but can wait until after a completed proof a concept.

To enable Secure Mode in Analytics.js, you pass in the secure variable by rendering it in your server-side templates. The secure field should be a SHA256 hash of your Castle API Secret and the user ID.

Here’s an JavaScript example of an identify call with Secure Mode being rendered with Ruby server-side templating language:

analytics.identify('1234', {
  email: '',
  createdAt: '2015-02-23T22:28:55.387Z',
}, {
  integrations: {
    Castle: {
      secure: '<%= OpenSSL::HMAC.hexdigest("sha256", "YOUR_CASTLE_API_SECRET", %>'

To use secure mode in your mobile app, you will need to first fetch the secure token from your server-side, for example:

def user_token(user_id)
  OpenSSL::HMAC.hexdigest("sha256", "YOUR_CASTLE_API_SECRET", user_id.to_s)

Requesting a risk score

Castle's adaptive authentication tells you whether to allow access, initiate a second factor of authentication, or log out the user.

Since all Segment calls are called asynchronously, you will need to use Castle's native SDKs to perform adaptive authentication.


Segment lets you change these settings on the Integrations page in your Segment account, without having to touch any code.

API Publishable Key

You can find your Publishable Key under Settings in the Castle dashboard. It should look something like this: pk_ozRgSnjfWG2xUsXNSqe46Y8F8DW68AAd.

Automatic Page Tracking

When you enable Automatic Page Tracking, Castle will track a page view whenever the URL of the site changes. We recommend using this option if you aren't tracking track page views on each page load.

When enabled, manual page calls will not be forwarded to Castle to prevent duplicates.

By default, the __cid tracking cookie is set on the current top-level domain (e.g., which includes all of your subdomains. If your authenticated area is located at a different domain, use the Custom Cookie Domain setting to change on which URL the cookie is set.