@sentinelsup/sdk

Official Node.js SDK for Maskbreak — network and device fraud signals for browser-SDK-backed visits, plus limited public IP intelligence.

Set up with AI (fastest)

Using Claude Code, Cursor, Copilot, or any AI coding assistant? Paste this one prompt and it wires the whole integration — frontend script, backend check, env var, and a test:

Fetch https://maskbreak.com/integrate.md and follow it to add Maskbreak fraud protection to this app — protect signup, login, and checkout. Start in watch mode (MASKBREAK_MODE). Read the API key from the server-only MASKBREAK_API_KEY environment variable; I will configure the secret separately. Never put it in client-side code. Then show me how to test it.

Never paste the key itself into a prompt: set it in your hosting secrets.

integrate.md is the canonical machine-readable integration guide, kept in sync with the live API.

Install

npm install @sentinelsup/sdk

Zero dependencies. Requires Node.js 18+ with built-in fetch. Other runtimes and edge bundlers are not covered by this package's test matrix.

Quick start

Add <script async src="https://maskbreak.com/assets/sentinel.js"></script> to the page with your form and class="monocle-enriched" to the form: it adds two hidden fields on submit, monocle and sentinel_fp. Your server forwards them:

const Sentinel = require('@sentinelsup/sdk');

const sentinel = new Sentinel({ apiKey: process.env.MASKBREAK_API_KEY });

// Start in watch mode: log Maskbreak's answer and let everyone through.
// When Events look right, set MASKBREAK_MODE=enforce and redeploy.
const MODE = process.env.MASKBREAK_MODE || 'watch';

let result = null;
try {
  result = await sentinel.evaluate({ token: req.body.monocle, fingerprintEventId: req.body.sentinel_fp });
  console.log('[maskbreak]', MODE, result.decision, result.reasons);
} catch (err) {
  console.log('[maskbreak]', MODE, 'check unavailable:', err.message); // evaluate() throws without a token
}
if (MODE === 'enforce' && (!result || result.decision !== 'allow')) {
  return res.status(result && result.decision === 'block' ? 403 : 409).json({ error: 'Verification required' });
}
// Watch mode, or an allow: continue with your existing handler.

A form that submits with JavaScript (fetch, React) calls await window.Sentinel.collect() before sending and adds its token and fingerprintEventId to the request. The full enforce policy (review, missing evidence, test and degraded answers) is in integrate.md.

Get a free API key (no credit card) at maskbreak.com/signup.

Since v0.3.3, new Sentinel() without a key reads MASKBREAK_API_KEY from the environment; the older SENTINEL_KEY and SENTINEL_API_KEY names are still read as fallbacks.

What you get back

Illustrative response. The VPN/proxy service name is returned only when known; otherwise it is null. Device fields require available device intelligence, not just a supplied event ID.

{
  decision: 'review',          // 'allow' | 'review' | 'block' — route on this
  risk_score: 65,              // 0–100
  isSuspicious: true,          // legacy flag; route on decision instead
  ip: '198.51.100.18',
  country: 'NL',
  network: {
    vpn: true, proxy: false, datacenter: true, anonymous: true,
    tor: false, residential: false, service: 'PROTON_VPN'
  },
  device: {                    // when fingerprintEventId resolves to device data
    antidetect: false,         // antidetect browser detected
    automation: false,         // bot / browser automation
    emulator: false, virtual_machine: false, incognito: false,
    ip_blocklisted: false, visitor_id: 'abc123', tampering_score: 0
  },
  reasons: ['vpn_detected', 'datacenter_asn']  // machine-readable codes
}

Try the live sample (same shape, no key needed): curl "https://maskbreak.com/v1/evaluate/sample?scenario=vpn"

Legacy details / deviceIntel fields are still returned for backwards compatibility with 0.1.0 integrations.

Frontend setup

Add the Maskbreak SDK to your frontend. One script loads both layers — network (VPN/proxy/datacenter) and device (antidetect/bot/tampering):

<script async src="https://maskbreak.com/assets/sentinel.js"></script>

<!-- Add class="monocle-enriched" to any form you want evaluated -->
<form class="monocle-enriched" id="checkout-form">
  <!-- The SDK injects both:
       <input type="hidden" name="monocle"     value="eyJ...">  (network)
       <input type="hidden" name="sentinel_fp" value="a1b2..."> (device) -->
</form>

Collect both and send them to your backend:

const { token, fingerprintEventId } = await window.Sentinel.collect();
fetch('/checkout', {
  method: 'POST',
  headers: { 'Content-Type': 'application/json' },
  body: JSON.stringify({ token, fingerprintEventId })
});

Examples

Stripe Checkout — block card testing

const Sentinel = require('@sentinelsup/sdk');
const stripe = require('stripe')(process.env.STRIPE_KEY);
const sentinel = new Sentinel({ apiKey: process.env.MASKBREAK_API_KEY });

app.post('/checkout', async (req, res) => {
  const { decision } = await sentinel.evaluate({ token: req.body.token, fingerprintEventId: req.body.fingerprintEventId });
  if (decision === 'block') return res.status(403).json({ error: 'declined' });

  const intent = await stripe.paymentIntents.create({ /* ... */ });
  res.json({ clientSecret: intent.client_secret });
});

Signup — block fake Google sign-ins

app.post('/auth/google', async (req, res) => {
  const { credential, monocle, sentinel_fp } = req.body;
  const ticket = await googleClient.verifyIdToken({ idToken: credential });

  const result = await sentinel.evaluate({ token: monocle, fingerprintEventId: sentinel_fp });
  if (result.decision === 'block') return res.status(403).json({ error: 'signup_blocked' });

  await createUser(ticket.getPayload().email, result.device?.visitor_id);
});

Custom policy with shouldBlock

// Keep the API's own blocks, and also block a VPN visitor whose device is
// already behind another of your accounts. The API alone answers review for
// that visit (a VPN is review; a shared device adds the multi_account_device
// reason without changing the decision). device.multi_account needs the
// accountId you pass and a resolved device event.
const blocked = await sentinel.shouldBlock(
  { token, fingerprintEventId, accountId: user.id },
  r => r.decision === 'block' || (r.network.vpn && r.device?.multi_account === true)
);

Burner-email check at signup

// Pass the signup email and Sentinel checks it against a continuously
// refreshed disposable-domain feed. A hit adds the disposable_email
// reason, raises risk_score, and escalates allow → review. The address
// is checked transiently — never stored or logged.
const result = await sentinel.evaluate({ token, email: req.body.email });
if (result.email?.disposable) {
  // e.g. require a real address before granting the trial
}

Look up an arbitrary IP — no browser token needed

// Batch scoring, log enrichment, server-side screening. Same key,
// same hourly quota as evaluate().
const info = await sentinel.lookup('185.220.101.34');
// info.verdict     → 'allow' | 'review' | 'block'
// info.risk_score  → 0–100
// info.signals     → { vpn, proxied, tor, dch, anon } (null when known:false)
// info.network     → { asn, org, country, city }

API

new Sentinel({ apiKey?, endpoint?, timeoutMs? })

Option	Type	Default	Description
apiKey	string	$MASKBREAK_API_KEY (then $SENTINEL_KEY, $SENTINEL_API_KEY)	Your key starting with sk_live_; required unless one of those env vars is set
endpoint	string	https://maskbreak.com	Override base URL
timeoutMs	number	5000	Per-request timeout

sentinel.evaluate({ token, fingerprintEventId?, accountId?, email? })

Returns EvaluateResult. Throws SentinelError on network/API failure — the error carries .status and .body.

• fingerprintEventId — requests device signals (tampering, automation, emulator, …). When the device is identified, device.times_seen, device.first_seen and device.returning describe its retained sightings across Maskbreak, not just your account. These records are pruned after 90 days of inactivity; first_seen is not necessarily the device's lifetime first visit.
• accountId — your own user id for this session; with an identified device, enables customer-scoped account linking (device.linked_accounts / device.multi_account). Links are hash-only, never cross-customer, and pruned after 90 days of inactivity.
• New device.customer_history reports distinct verified events, first/latest visit and associated account counts only for your customer account over a rolling 90-day window. Fresh live-key events start this history; test keys and duplicate event submissions do not add to it. Derive accountId from your backend's authenticated session, never a browser-claimed account ID. Shared devices are not automatically fraud. Legacy fields above retain their meanings.
• An optional, default-off GPU evidence beta is available over raw HTTP with explicit browser collection. Published SDK versions may omit gpuEvidence; use the documented HTTP flow. It does not change fraud decisions or automatically link devices.
• email — adds email.disposable to the response; burner domains escalate allow to review.

sentinel.lookup(ip)

Returns LookupResponse for a public IPv4/IPv6 address (wraps GET /v1/lookup/{ip}): a verdict, risk score and limited public-feed evidence from cloud-hosting ranges and Tor exit lists. Legacy VPN/proxy fields do not establish complete coverage. Use evaluate() with a browser SDK token for VPN/proxy evidence and service naming when known. known: false, false signals or an allow verdict are not a safety guarantee. Network metadata may be null. Shares the per-key hourly quota with evaluate().

sentinel.shouldBlock({ token, fingerprintEventId? }, predicate?)

Convenience: runs evaluate() and returns a boolean. Default predicate is r => r.decision === 'block' (honors your dashboard rules and allow/block pins). Pass your own to build custom policies.

accountId, email, and lookup() require v0.2.1 or later (npm install @sentinelsup/sdk@latest) — the older 0.1.2 silently ignores accountId/email.

Testing

Deterministic test tokens exercise every decision path from a terminal — authenticated and rate-limited like real calls, but never billed, stored, or webhooked (responses carry "test": true):

await sentinel.evaluate({ token: 'test_vpn' });   // → engine decision: 'review' (your rules/pins may override)
await sentinel.evaluate({ token: 'test_clean' }); // → decision: 'allow' path
// also: test_proxy, test_datacenter, test_tor

• No account yet? The public sandbox key sk_test_sandbox answers the same test_* tokens with the same shapes — no signup, nothing stored.
• CI / staging with real traffic: every account also has a personal sk_test_… key (Settings → API keys) that runs the complete live pipeline — device intelligence, your rules and exception pins. Its events are marked test, kept out of your stats and never fire webhooks; its checks count toward the monthly allowance (the fixed test_* tokens and sk_test_sandbox do not). It is exempt from the account's IP allowlist.

Rate limits

Visitor checks (evaluate()) are counted per calendar month in UTC, with an hourly cap: Free — 10,000 a month, up to 1,000 an hour, no credit card; paid plans from €29 a month (pricing). IP lookups (lookup()) have their own monthly allowance, 10× the plan's checks (100,000 on Free). A used-up month answers 429 with code: "monthly_quota_exceeded" and Retry-After until the 1st; there are no overage charges.

On 503 with .body.code === 'storage_unavailable', the key could not be checked at that moment (not an invalid key; 401 is): retry later and apply your outage policy meanwhile.

On 429, the thrown SentinelError has .status === 429. This SDK exposes status and body, not HTTP response headers. If your integration needs Retry-After or X-RateLimit-*, use raw HTTP and read those headers from the response. Use bounded backoff and an endpoint-specific fallback; an unavailable check is not an allow verdict. Approved public-interest keys have no per-key hourly cap, but independent endpoint and abuse-protection limits still apply.

The current evaluate() helper requires a non-empty token and does not serialize tz. Raw HTTP accepts missing or empty tokens as degraded evaluations and supports the timezone returned by Sentinel.collect(). Use the HTTP reference for those paths; missing network evidence does not prove a visitor is safe.

Development checks

npm ci --ignore-scripts
npm test
npm pack --dry-run --ignore-scripts
npm audit

Tests use local fixtures, not production keys. CI checks Node.js 18, 22 and 24. These commands do not publish a package.

TypeScript

Full types ship with the package. Importing Sentinel gives you the class plus EvaluateResult, DeviceIntel, EvaluateDetails, and SentinelError types.

import Sentinel, { EvaluateResult } from '@sentinelsup/sdk';

What Maskbreak detects

SDK-backed visits can supply VPN/proxy, cloud-hosting and Tor signals, with VPN/proxy service names when known. Available device intelligence adds browser tampering, automation, emulator and virtual-machine signals. Coverage depends on the evidence available; these are not guarantees of detecting every product or visitor. Bare-IP lookup is limited to public cloud-range and Tor evidence.

Related

• Python SDK — sentinelsup on PyPI
• Free IP lookup tool — maskbreak.com/ip-lookup

License

MIT © Sentinel Edge Networks LTD

Links

• Website — maskbreak.com
• API docs — maskbreak.com/api
• Blog — maskbreak.com/blog