Detection Signals
Beyond the core detection features, Sentinel exposes a set of supporting signals — each usable standalone via its own API endpoint, and each feeding into the overall risk score used by Adaptive Captcha and the Classifier.
IP Resolution
Turns an IP address into geolocation and risk data — hosting-provider, proxy, Tor, and malicious-IP status — cross-referenced against Threat Intelligence.
POST /v1/ip
{ "ip": "1.2.3.4" }This is the feature; which external services actually resolve the data (MaxMind, ipinfo.io, Cloudflare, etc.) is configured separately — see IP Resolvers.
Header Entropy
Available since v1.31.0. Tracks how many distinct combinations of device-identifying headers a single device (per IP) sends over time, to catch attackers rotating headers to impersonate multiple different devices:
Accept-LanguageSec-CH-UASec-CH-UA-MobileSec-CH-UA-PlatformUser-Agent
It also scores User-Agent commonality — how common a given User-Agent string is against a known-identifier database — from low (uncommon, bot-like) to higher for widely-used browsers.
Scoring: each new header-combination profile seen from a device adds 1 point of risk/penalty by default, scaled by headerEntropyRiskFactor.
Configuration (via a Security Group's set rule, see Schema):
| Field | Default | Purpose |
|---|---|---|
headerEntropyLimit | 10/4h (with Autopilot) | Rate limit on distinct header combinations before the request is rejected with 429. |
headerEntropyRiskFactor | 1.0 | Multiplier (0.0–10.0) applied to the risk added per new combination. |
| Variable | Default | Purpose |
|---|---|---|
HEADER_ENTROPY_MAX_ENTRIES | 100 | Max header-combination hashes stored per IP. |
Language Detection
Identifies the language of a piece of text — over 160 languages, roughly 3ms round-trip for short inputs.
POST /v1/language
{ "text": "..." }Returns detected languages ranked by probability. Input over 400 characters is truncated; detection is more accurate on longer text, though 2–3 word phrases are often enough for major languages — submit a full sentence or paragraph where you can. This feeds the Classifier's UNEXPECTED_LANGUAGE rule (see Classifier).
Links and Redirects
Puts a verification challenge in front of any URL — similar to Cloudflare's verification/interstitial pages. Visitors hit a short link at /link/:slug, complete a challenge, and only then get redirected to the real destination.
Creating a protected redirect
- In the admin interface, go to Redirects → Create Redirect.
- Give it a name.
- Set the destination URL.
- Select the API Key whose Security Group governs the challenge type and rate limiting shown on this link.
Custom fields
A protected redirect can require custom input fields before continuing — all fields are required. Field values can be substituted directly into the destination URL with {field_name} syntax (e.g. {email}).
Fields can also be evaluated by AI Security Rules for more nuanced checks — see Usage with redirects.
An optional footer link lets you reference your privacy policy or terms of service on the verification page itself.