metamask-extension/app/scripts/controllers/transactions/lib/recipient-blacklist-checker.js

import Config from './recipient-blacklist.js'

/** @module*/
export default {
  checkAccount,
}

/**
 * Checks if a specified account on a specified network is blacklisted.
  @param networkId {number}
  @param account {string}
*/
function checkAccount (networkId, account) {

  const mainnetId = 1
  if (networkId !== mainnetId) {
    return
  }

  const accountToCheck = account.toLowerCase()
  if (Config.blacklist.includes(accountToCheck)) {
    throw new Error('Recipient is a public account')
  }
}