Well, Target knew which ones. So the banks know now.
No they don’t. They know 80Million were taken. but they don’t know which they were. They’re trying to figure that out right now.
Target's not supposed to be storing the full account numbers. They're only allowed to retain the first six and the last four. That, and they also have the authorization codes and the exact date and time.
So, Target doesn't have the full list (except for their own store card, the REDcard™). However, the banks could conjure up the list by passing their databases and flagging charges made by Target customers in the affected time period.