1b) Numbers only. See for example http://en.wikipedia.org/wiki/Address_Verification_System and understand that "street address" just means whatever numbers are there at the beginning of the address. Also understand that this is frequently incredibly low quality data, all you can really rely on is the zipcode match part, trying to do any better will result in a lot of false negatives.

2) There are multiple names for this. In the beginning, on mag stripes, CVV/CVC (name varies by network) was developed and it was a way to validate that somebody didn't build a mag stripe based on just knowing the card numbers - it's data that exists only on the mag stripe and is not printed on the card. Then, CVV2/CVC2/CID/etc was developed and it is a way to validate that somebody has seen the actual card - it is data that is printed on the card but is not in the stripe. People usually don't know about the difference and are talking about CVV2/CVC2 when they say CVV or CVC. The key thing that makes this work is that merchants are restricted from storing the CVV2/CVC2/CID data (and they already weren't supposed to store mag stripes, so CVV/CVC also), so if somebody gets a database dump of a bunch of credit cards it shouldn't have CVV2/CVC2 data in it. It also doesn't come for free from an automated skimmer because it isn't on the mag stripe. And, way back in the day, it wouldn't have been on the carbon copies because it was in flat type. So, this really does add some security to a transaction. So what it does for chargeback protection is make it more likely that you are dealing with someone who physically has the card in front of them, because that little bit of data is harder to steal than the other bits of data. It still doesn't let you win a chargeback - for that, you need a signature, which you won't have if you're doing ecommerce, so you'll lose. It just makes the chargeback less likely in the first place.

Additionally, if you are classified as doing ecommerce, some issuers will simply decline any transaction that doesn't have CVV2/CVC2. Varies by merchant category and by issuer.

3) Don't know, I processed cards in America. Debit cards when used with PIN have a completely different technology behind their security, and a completely different set of laws covering them than credit cards do, but I don't know about chip-and-pin.

4) Don't know, because Internet.

First, names are not really checked.

For addresses, usually only the number (and sometimes just first three digits) are checked as well as the zip.

Generally the processor tries to decline as few txns as possible and instead deliver the information to the merchant to make a decision. The merchant can usually pre-configure error codes that it would like the processor to decline. This might be preferable to the merchant from a cost-saving standpoint as well as not needing to "void an auth" in order to free up the cardholders spendability.

The idea behind CVVs is that merchants are disallowed from storing them so they are far less likely to be included in stolen credit card databases. Thus, requiring them significantly decreases fraud risk. And, yes, many gateways/processors charge more for missing or incorrect CVVs.

It's harder to "steal" a chip card since the information is not sitting on an easy-to-read mag-stripe. It's not clear that chip cards would have avoided the Target thing since the fraudsters infiltrated the terminal software. I'm guessing more current terminals/software is simply harder to compromise. "Chip & pin", as is widely used in places such as Canada and Europe, might help a bit since you would need the PIN to shop off-line. But it would have minimal effect for online shopping since PIN is typically not requested.

The reason we still sign receipts and yes, you still see a carbon copy here and there, is mainly because it protects the merchant if the cardholder does a "chargeback". Merchants typically store the receipts and only turn them over if a chargeback is received. Showing the signed receipt to your processor will usually absolve you from any loss.

I think the above is accurate or close to.

Chips are the same thing - it reduces the fraud risk, thus reducing your processing fees. the carbon imprint is just like a chip - physical proof that the card was present during the transaction. card-present environment is a much lower risk profile than card not present environment, the difference between the two is often a full percentage point in processing fee.

The address verification is not a regex, it's just a simple lookup. Most merchants don't actually do address verification though because it is fairly expensive.

CVV is also known as card not present number. Historically it was printed on the back of the card, or on the front using unraised type. This way, if an impression of a credit card was taken (using one of those old fashion swipe back and forth machines), the CVV number would not be included in the impression. This provided some protection for card owners, as it prevented a merchant from using the credit card number obtained from an impression to say place an order using the CC over the phone. This is why you're required (or it's recommended) that you ask for the CVV number for any transaction where the card is not present.

What we found was a huge increase in people typing 'Visa' or 'Mastercard' into the 'Name on the card' field (whatever the field was called, I don't remember). People were so used to having to provide that information that they began to provide it in lieu of providing the cardholder name at all.

Think about that for a second; they stopped putting their own name anywhere on the credit card form, and instead started putting the card type in that field. Conversion went down, customer service issues went up.

We added the field back to the form, even though it was never checked and did nothing, and it resolved the issue.

Also, many ATM cards (a foreign concept to this European until very recently) overlap with Visa ranges. In fact, my ATM card parses exactly as a Visa number. It even has the Visa trademark mentioned on the back. No, you can't use it for online transactions. Apparently, Visa Debit is not a thing in Canada ...

My point is, showing wrong UI is often worse than clunkier UI.

Heads up: If you're in (say) Europe or UK, then American Express and Discover aren't a "big card issuer"

It helps that more savvy ecommerce sites are moving to this model so more and more users are familiar with the experience.

I'm hoping someone from ActBlue's dev team sees this and can jump in. They run a lot of fascinating tests on credit card forms.

I doubt there's a reasonable explanation as to why a CC field can't contain dashes or spaces. I'd love to hear one but I doubt there is one.

Poor Input Validation

Basically whoever was behind making the site couldn't be bothered dealing with those cases and just made them illegal options. Makes you wonder what other corners were cut.

Source: I run an e-commerece site and have written checkout flow.

And I can't review in a single glance whenever I typed everything right.

  function validateCC(ccNumber) {
    var ccNumber = ccNumber.replace(/ /g, '');

    console.log(
      /^3[4|7]\d{13}/.test(ccNumber) ? 'AMEX' :
      /^6011\d{12}/.test(ccNumber) ? 'Discover' :
      /^5[1-5]\d{14}/.test(ccNumber) ? 'MasterCard' :
      /^4[\d{12}|\d{15}]/.test(ccNumber) ? 'Visa' : 'Unknown',
      ccNumber,
      ccNumber.split('').reverse()
        .map(function (v, i) { return v * (1 + i % 2) })
        .reduce(function (agg, v) { return agg + v; }, '').split('')
        .reduce(function (agg, v) { return agg + +v; }, 0) % 10 === 0 ? '(valid)' : '(invalid)');
  }