Poisoning firewall

The firewall is the real anti-poisoning defense: a victim sends to a lookalike on purpose, so locking funds afterwards does not help. Only refusing does. It runs before anything is signed.

Check a recipient

import { check } from '@ctrl-arcz/sdk';

const report = await check(sender, target, { client: publicClient });
// report: { level: 'safe' | 'warning' | 'block', reasons, complete }

'safe' | 'warning' | 'block'

The worst severity found. block must stop the send.

RiskReason[]

Each with a code, severity and human message.

boolean

True only when every data source answered. An incomplete check never reports safe.

What it catches

Code	Severity	Meaning
`LOOKALIKE_ADDRESS`	block	Matches the first/last characters of an address you have paid, but is different.
`ZERO_VALUE_BAIT`	block	The target planted itself in your history with a 0-value transfer.
`DATA_UNAVAILABLE`	block*	Your payment history could not be fetched, so a lookalike cannot be ruled out.
`NEW_ADDRESS` / `FRESH_ADDRESS`	warning	No history, or minted in the last 24h.
`KNOWN_COUNTERPARTY` / `VERIFIED_RECIPIENT`	safe	You have paid this exact address, or a protected transfer to it settled.

Fail-closed. When the sender’s payment history is unavailable, the lookalike rule cannot run, so an unverified target is blocked, not waved through. A firewall that degrades to “looks fine” when its data source is down is worse than none.

A warning looks different from a block on purpose: it explains and lets the user decide, because a brand-new recipient is the most common legitimate payment there is.

Gate a send on it

import { check, shouldBlockSend, defineConfig } from '@ctrl-arcz/sdk';

const config = defineConfig({ onWarning: 'block' }); // or 'proceed'
const report = await check(sender, target, { client: publicClient });

if (shouldBlockSend(config, report.level)) {
  // show report.reasons, refuse the send
}

It is already on inside `sendProtected`

You do not have to remember to call it. sendProtected runs the check itself and throws RiskBlockedError on a block. Opt out per call only if you already gated:

await sendProtected(clients, params, { skipRiskCheck: true }); // you already ran check()
await sendProtected(clients, params, { config });              // its onWarning decides

It runs everywhere money leaves

The same check gates every outbound path, not just the send form: a protected send, a private payment’s target, each subscription pull the co-signer authorizes, and the bridge’s destination. One rule engine, one verdict, one explanation.

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Poisoning firewall

Check a recipient

What it catches

Gate a send on it

It is already on inside `sendProtected`

It runs everywhere money leaves

​Check a recipient

​What it catches

​Gate a send on it

​It is already on inside sendProtected

​It runs everywhere money leaves

Check a recipient

What it catches

Gate a send on it

It is already on inside `sendProtected`

It runs everywhere money leaves