Hi Jack:
In our system, we wrote code that checks the users address, IP addresses, email addresses, their telephone number. The program checks this against our blacklist. We have found that some idiots will use a phony name or a different email as an example. However some of their information is always the same.
Also in our program we have special notes that are associated to each customers in the database. We can add or edit these notes. You might want to add this into your code.