1. 概要
2016年，AmEx 成立了 RAT （Rewards Abuse Team）部門，專門嚴打各種不合他們的規矩拿點數的活動。當時，我們就有專文介紹：這裡。
到現在，3年過去了，這個 RAT 的活動也越發被大家了解，甚至一些了解 RAT 運作的人也偶爾在各個信用卡博客論壇發言，讓大家對於 RAT 主要逮的活動更加明了。
本文就和大家聊一聊最近一點新的小道（非官方）消息。當然啦，AmEx 官方肯定是不會告訴我們他們在做什麼和要做什麼的，只是有人在英文博客上的留言，但是感覺這個留言還是有一定道理的。
2. 起因
事情的起因是最近 AmEx 對於過去1年內self-refer獲得點數收回，緊接著又有一些人被 AmEx 殺全家（關所有卡）：文章在這裡。Reddit 上有人做了調查和分析（這裡），認為主要觸發原因可能是
- Self refer 點數收回
- 擁有超過1張同樣的 AmEx 卡（比如，有人有2張甚至3張金卡 Gold）
RAT 應該是通過這些因素來篩選持卡人，如果他們覺得風險較高或者擼得太過分，就會關卡。
3. 可怕之處
殺全家（關所有卡）其實別的銀行更喜歡，比如Chase，各種原因殺全家：專文在這裡。
但是 AmEx 殺全家的可怕之處是他家這一行為顛覆了大家對他家的認知。以前，如果大家有不合他家喜好的行為，AmEx 通常先對於持卡人進行一次 Financial Review，如果收入可以通過他家的 Financial Review，所有卡都可以保留並正常使用。對於 AmEx Financial Review，我們有專文（這裡）。
也就是說，歷史上，AmEx 很少直接殺全家（當然，也有個別比較過分的被不經過 Financial Review 直接殺全家，但是非常非常少見），都是 Financial Review 貓捉老鼠玩一玩，過了就不殺，只有過不了 Financial Review 才殺全家。但是這次，AmEx 對於這些可能違反了他們一些條款的持卡人，不再進行 Financial Review，直接殺全家。也就預示著，被 RAT 盯上的持卡人，是有可能不進行 Financial Review 就直接殺全家的。
可怕之處就在此了：Financial Review Team 可怕，但是還是講道理的，只要有美國的稅表，申請卡的時候收入和稅表基本一致，就幾乎肯定可以通過 Financial Review；但是 RAT 完全不給持卡人機會，直接就關所有卡了，持卡人連申訴的權利也不會有。
為了避免被 AmEx RAT 直接殺全家，大家不得不了解一下 RAT 究竟在幹什麼，他們根據那些不合適行為殺全家。
4. 新消息（非官方）
在 DoC AmEx 殺全家文的回復里，有個ID是 RAT Poison 的讀者回復了一些他知道的關於 RAT 的信息。雖然我們不清楚這個人是不是和 AmEx 相關的人，但是他說的確實有一定道理和借鑒意義。RAT Poison 的回復在這裡，為了保留一些這個回復做參考，我們把他的回複復制在這裡：
- I won』t say why or how, but I have insider info from RAT on what』s behind all this. This shutdown is part of a series of upcoming shutdowns. This week』s was a beta test for a new machine learning model specifically designed to target churning activity through unsupervised learning. Amex data scientists are improving an evolving neural network model that identifies churning behavior as it happens, and then assigns risk scores that factor in to anti bust-out or fraud scores. They』re treated the same, those all have different scores but their values affect your overall risk/reward score for Amex. If that overall score reaches a certain threshold (which they』re still experimenting with what exactly it will be), you will get shut down. What they』re doing is based on the same ML models that are used at Amex for AML and fraud prevention. The shutdowns will happen in small waves because one giant hit would be a massive drain on resources and disruption to their overall business, including drawing negative public attention outside of the churning community. That would scare people who are profitable but think they』re winning. They are also incrementing shutdown waves because of the resource usage it takes to identify accounts and assign a score based on the new indicated risk factors. When shutdowns are triggered, they begin combing through the new dataset. Right now, the model only looks back two years.
- The clawbacks on self-referrals were a pilot program to this week』s events, not an entirety separate event. The same model that identified self-referrers was used for these shutdowns.
- I』ll report back when I hear more info.
- Also, I should add that if you had self-referrals clawed back, you』re already in the main data set. Those who were hit by the clawback were flagged as the highest priority for the model to comb through because of the strong correlation to proven churning/gaming behavior. Self-referrals were like a litmus test for who will be the low-hanging fruit for them to cut. As they tune the model to identify more positive activity correlations with churning, it will get more specific. Combing through level 3 data will become more prevalent in identifying churners, especially true if you have transactions from GCM and other obvious sites in your transaction history. If you were hit in the clawback but weren』t shut down this time, be cautious that you』re in their crosshairs. From what I』ve learned about the model, the inferred course of action here to avoid a shutdown is to not do anything with Amex except organic spend on your existing cards. Don』t carry a balance, no more MS, and no new cards. Keep in mind that the anti-churning model is fundamentally based on the neural architecture of their anti-fraud model.
- PS I』ve read many comments loosly speculating about what RAT is. RAT isn』t a bunch of guys in India who are manually combing through the accounts with high MR balances, or checking referral sources for validity, etc.. This isn』t true. 「RAT」 is two data science and machine learning engineers in Phoenix who transitioned from the Amex fraud prevention team. There are two other engineers who have shared responsibilities with RAT and other anti-fraud teams.
- The Hilton Aspire no AF link had absolutely nothing to do with these shutdowns. It』s a pure coincidence. The portfolio of recommended accounts to be shut down was sent off for approval more than a week ago. RAT doesn』t shut down accounts. They provide tranches of customer accounts suspected of abuse – along with correlating data. Those tranches go to evaluation from non-engineering management; who are the decision makers on shutting down a tranch of accounts or enacting other penalties. This is new to them and it』s somewhat uncharted territory, the speculations on here and on Reddit that they』re winging it are accurate. Their plan is to cut losses and effectively disable Amex churning first, then deal with the fallout afterwards. They』re legally within their rights so shutdown approvals are not made on a legal basis.
他的回復里有幾個要點，我們總結一下：
- AmEx RAT 正在使用神經網路機器學習模型對 AmEx 掌握的大數據進行分析，從而抓出 Abuse Rewards 的人。
- AmEx RAT 的想法是，使用他們的模型給每個持卡人一個風險（risk，拿了人家多少點數）和收益（reward，給 AmEx 貢獻了多少收入）評分，如果這個評分高於某個閾值，RAT就會殺全家；當然，RAT 仍然在調試模型，找出合適的閾值：他也不想誤殺了給 AmEx 帶來收益比較高的持卡人。
- 現在的Self refer是第一批抓出來的，因為 Self refer 和 churning 有比較直觀的聯繫。
- 未來，RAT 會優化他們的機器學習模型，一波一波的抓出 Abuse Rewards/churning 的持卡人，直接殺全家。
- 被因為 Self refer 收回點數的持卡人要尤其注意，這些持卡人已經在 RAT 的重點觀察名單里，如果再犯別的，就有可能被殺全家。
- 近期的未來，RAT 會在模型里加入 Level 3 data（就是持卡人在商店每筆交易的具體內容，包括買了啥東西），對於買 Gift Card 的，是重點觀察對象。
- 最近的 Hilton Aspire 免第一年年費鏈接和殺全家沒關係（我們的文在這裡）。
- 有一點好的地方：RAT 的模型只查看過去2年的數據，持卡人在2年之前的行為模型就不考慮了。
他建議的幾點安全行為：
- 不要申新卡。
- 不要製造消費（Manufacture Spending），就是不要買現金等價物，Visa Gift Card 之類的，不要在 GiftCardMall 之類的網站消費。
- 每月付清賬單。
5. 我們應該怎麼做來避免被 AmEx RAT 殺全家
綜合上面的信息，我們這樣做也許可以幫助避免被殺全家
- 一定不要 Self Refer。
- 之前申請過的卡，一定不要再次申請。
- 不太現實的一點：不要申新卡。也許可以折中一下，如果持有若干張 AmEx 卡以後，盡量少申新卡。
- 不要製造消費（Manufacture Spending），就是不要買現金等價物，Visa Gift Card 之類的，不要在 GiftCardMall 之類的網站消費。
- 每月付清賬單。
6. 總結
AmEx 也加入了直接殺全家的銀行大家庭，以後申請和使用 AmEx 卡大家都要再更當心一些，不要惹了 AmEx RAT。
註明：本文主要目的是讓更多中文讀者了解 AmEx RAT，規避風險。本文參考了 FrequentMiler ，他們更早注意到RAT Poison的回復並分析，在此致謝！