Scammers may try to bypass traditional security features when paying by debit or credit card. Some "attempt" to run the card through the reader until an error message prompts for manual entry. Others claim to have forgotten their card and then ask the clerk to manually enter the card numbers instead. Scammers then provide a number they have memorized.
Manually entering numbers in this situation in never a good idea, and it could leave you responsible for potentially fraudelent charges. The best way to avoid this type of scam is to require customers to physically provide a debit or credit card for payment.
