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Comment by MiddleEndian | Hacker News Reader

lol on a much lighter note, for many years I used to use 111-111-1111 as a general phone number for CVS card discounts. It stopped working several years ago though.

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As a Canadian I was lost and confused when visiting the States (in the before time) and a gas pump asked for my zip code. So I put in the one and only zip code I know. I bet you can guess.

Glad you could come visit from Beverly Hills ;)

EDIT: actually, depending on your age and what you watched on TV, maybe you were visiting from Boston?

I used to use that one too, but you're supposed to put the 3 numerical digits of your postal code followed by 00. (I have no idea how you're supposed to know that though.)

Really? Or does that just work because it's numbers? I can't imagine how that's useful because without the letters the same 12300 could be in Vancouver or Montreal couldn't it?

I don't know much about credit card validation, but I have the impression that the zipcode is just one more correlation that tells them you're more likely to be the real owner of the card.

If the 3 numbers I type match the 3 digits of the owner's postal code, it's probably a reasonable signal that I'm the owner (even without the letters).

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Close!

https://youtu.be/XanjZw5hPvE?si=Og-5iyLzjxebT6EF

I was inputting for ages.

Did it work?

It probably did. I was in the us this summer and was similarly confused that the pump wanted a us zip code for a foreign card. I input the zip for the address i was staying at and it worked...

Huh. I'd always assumed the zip code was validated against the card's billing address but maybe it's actually for some kind of market research. I'll have to try myself.

Following up: I tried a valid but incorrect zip code recently and the transaction was declined. Presumably this is because there is a valid one associated with my account?

Yeah. Random numbers wouldn’t but it did. I assumed it had to be a valid zip code.

This reminds me: I've noticed that Starbucks now requires a few pieces of information to use their WiFi network. One is email and they are doing some sort of validation which will reject emails like whoopsileanedonxxxxxxxx@aol.com but will accept other, legit AOL emails. How are they deciding what is/not a valid email? Are they using a compiled list of emails that have been seen in the wild? What if it's a brand new address, though? Presumably AOL isn't exposing a service for them to use in realtime. I haven't tested this extensively or with other providers.

It's obvious that they care (to some extent) that they're getting valid emails, so why not use a basic regex on the FE and an OTP which gets sent to the provided address?

They can connect to a mail server and pretend that they are going to send a message and the server would reject the invalid recipient email.

I had no idea this was possible. This sounds almost like an HTTP OPTION request. I'd love to find an example of client code which does this.

You're looking for the SMTP VRFY and EXPN commands. However implementation is very hit-or-miss. In the good ole' days of the internet, VRFY was widely implemented. Then spammers realized they could connect to a mailserver and do a form of a VRFY dictionary attack to find valid addresses, so it stopped being supported.

> why not use a basic regex on the FE and an OTP which gets sent to the provided address?

I can't prove I control an email in order to use your wifi, if I can't use your wifi.

Some wifi networks give you a limited number of minutes online during which you need to click a verification link they've emailed you in order to not get cut off.

That's a great point. I guess I'm so conditioned to various 2FA methods that I take some amount of access (i.e. mobile) for granted.

Use *@example.com, it usually works.

XXX-867-5309 still works everywhere I try it, where "XXX" is the local area code.

I have also used XXX-555-1212, and it has worked everywhere.

I used 888-888-8888 at Target yesterday. Shhh.

Lookup the stores phone number of maps. That usually works.

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