Good recommendations noted above.
Documentation of the implementation process and your methodology for setting rule thresholds and customer risk scoring factors is essential. Regulators and auditors will be looking for this documentation during exams/audits.
Ask the other bank if they have identified any monitoring gaps - transactions that the system does not capture or does not effectively monitor. examples would be IAT ACH, Foreign Wires, Loans, Letters of Credit, prepaid cards etc. Even if you do not have some of the products now, you may find you bank adding new products down the road.
Independent validation of the system will be required. You may want to begin the RFP process for that soon. You will want the validation to be performed about 6 months after going into production with your system. This will allow enough time to build sufficient data to test during the validation. Also make sure your validation includes Rule Tuning & Optimization and, if you are using the customer risk scoring part of the system, validation of the Customer Risk Scoring model.
Also regarding validations, cheaper is not always good. I have seen a couple of these rejected by examiners and had to be redone by another third party.
One thing many banks do not know is that there are some firms who have specialists that can assist the bank with the system implementation process. Many times we feel that the vendor knows what they are doing and will set it up properly. This is far from the truth. They will install based on defaults and leave it up to you to do the rest. Since each bank is different, the defaults will not provide you with an efficient system. You will not have enough knowledge of the system to do this effectively. It will cost some money, but well worth it.
One other suggestion is to make sure your Sr. Management understands...This system will not reduce your workload. It will greatly increase and you will need resources (read as people) to assist with reviewing alerts, documenting investigation results and filing SARs.
Good Luck!
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CAMS, AMLP, AKC, K-9