When making a purchase at a participating online retailer, Verified by Visa requires you to input an additional password to confirm your identity before completing a transaction.
You can activate Verified by Visa on your card at Visa's website, with your card issuer or when prompted with the option at a participating retailer.
Visa points out that when you sign up for Verified by Visa, you submit a "personal message." This message appears in your Verified by Visa window when you are about to make a purchase, to offer further validation that you are safely and securely inputting your password.
Visa notes that if you suspect someone has stolen your Verified by Visa password, you should immediately contact your card issuer.
As of February 2010, over 100 online retailers are part of the Verified by Visa program. They include, but are not limited to, WalMart.com, Toys R Us, Office Max, Dell and Delta Airlines.