PROTOPHREAK on Nostr: I can try to explain based on personal experience. Bank API's can be very chatty. One ...

I can try to explain based on personal experience. Bank API's can be very chatty. One of the most common things a KYC exchange will be able to see is your balance. They can refresh and see your balance at any time for the associated bank account. This is often used for anti-fraud efforts and also to see if the bank account is significantly negative. If its not too negative the exchange may let you run the transaction anyways and then freeze the account until you are able to bring your exchange account out of negative.

This is the tip of the ice berg. The level of detail available to any exchange or really financial tech service is incredible.

My advice is where possible, only connect your debit or credit card. If you have to connect your bank, remove the connection after you are done. Additionally, sometimes banks force API's to make you log in with your actual bank password (WTF????) so be sure to change that once in a while. Doing so will kill any API connections to lingering financial service accounts you may have forgotten about.