> ## Documentation Index
> Fetch the complete documentation index at: https://developer.hellgate.io/llms.txt
> Use this file to discover all available pages before exploring further.

# Overview

> Encode fraud and business rules and evaluate every transaction against them in real time.

Specter is a low-latency, high-throughput decision engine built for the [Composable Payment Architecture](/platform/cpa). It combines fast in-process rules with backend integrations to external risk services for payment fraud prevention. By ingesting transaction data over time, it continuously improves detection.

## Role in the Hellgate Cloud Platform

Specter gives you a straightforward way to encode complex fraud detection and prevention logic. It is built for composition and can be extended through [Link](/products/link/overview) to connect to virtually any external fraud-detection service.

Like every service on the Hellgate Cloud Platform, Specter can be used standalone or in composition with other services.

## Main features

Specter combines three sources of signal and control in a single ruleset.

<CardGroup cols="1">
  <Card title="Local rules" icon="sliders" href="/products/specter/concepts/rule-engine" horizontal>
    <Badge size="xs" color="blue">Standard Feature</Badge>

    Conditions and velocity counters evaluated inside the engine — boolean
    expressions over the decision context plus rolling-window counts per card,
    customer, device, or IP. No external calls, evaluated in-process for minimal latency.
  </Card>

  <Card title="Blacklist" icon="ban" href="/products/specter/concepts/blacklist" horizontal>
    <Badge size="xs" color="blue">Standard Feature</Badge>

    Field-based blocking with optional TTLs. Entries are managed through the
    Admin API or auto-populated from [lifecycle
    events](/products/specter/concepts/lifecycle-events) such as chargebacks and
    fraud reports.
  </Card>

  <Card title="Backends" icon="plug" href="/products/specter/concepts/backends" horizontal>
    <Badge size="xs" color="blue">Standard Feature</Badge>

    External risk engines — reached through a Link integration and invoked from
    backend rules to assess a transaction.
  </Card>
</CardGroup>

## Integration patterns

Specter offers two ways to put a fraud check in front of authorization. Both evaluate the same rulesets and
return the same outcomes — they differ in **where the integration lives**. See the
[integration overview](/products/specter/integration/overview) to choose the right approach for your situation.

<CardGroup cols={2}>
  <Card title="Decision API" icon="code" href="/products/specter/integration/via-api">
    Your system calls `POST /api/decisions` before authorizing and branches on
    the result. Full control over the payment flow, with the richest request
    context.
  </Card>

  <Card title="Interceptor" icon="diagram-project" href="/products/specter/integration/via-interceptor">
    Specter sits inline as a transparent proxy in front of your acquirer —
    forwarding approved transactions and returning a configured response for
    those it flags. Adds fraud checks with no backend changes.
  </Card>
</CardGroup>

## Next steps

<CardGroup cols={2}>
  <Card title="Plans & Access" icon="key" href="/products/specter/plans-and-access">
    Dedicated infrastructure, tiers, and how to obtain a Specter instance.
  </Card>

  <Card title="Authentication" icon="lock" href="/products/specter/authentication">
    Authenticate to your instance, and the scopes that gate each endpoint.
  </Card>
</CardGroup>