In an effort to help protect merchants from fraud, the card issuing companies make excellent information available to merchants.
Visa
Take the Order but Don't get Taken In
Five Important Things You Should Know About Unembossed Visa Cards
5 Simple Steps to Safer Key-Entered Transactions
American Express
American Express Merchant Reference Guide - U.S.
American Express Fraud Best Practices Page
Discover
Discover Fraud Identification Procedures
MasterCard
