| Credit Card Security Digits [message #379938] |
Di, 11 April 2006 11:40 |
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The final 3 characters appearing on the reverse of the card. What is the
purpose of these?
Since they are now routinely requested for postal and telephone (as well as
online) transactions, any value as an additional security measure is
(presumably) very limited.
These details in combination with the other credit card details, customer
address and the service or items being purchased are going to be known to
any number of call centre and other clerical staff across the country or
overseas, fertile ground indeed for potential ID theft.
Incidentally, there is presumably an algorithm that computes or validates
the security digits against the card number itself, or do the merchants
validate the details directly with their bank?
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| Re: Credit Card Security Digits [message #379946 ] |
Di, 11 April 2006 13:00 |
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Gunslinger wrote:
> The final 3 characters appearing on the reverse of the card. What is the
> purpose of these?
They are to prove that the actual card is in the shopper's possession.
The point is that these figures are never printed on transaction
receipts, and therefore the genre of fraud eliminated is that of
people rummaging through bins for such receipts.
> Since they are now routinely requested for postal and telephone (as well
> as online) transactions, any value as an additional security measure is
> (presumably) very limited.
They ought to be required *only* for phone and online transactions, and
*never* for postal ones. The whole point, surely, is that they should
never be written down, and cannot therefore be stolen.
> These details in combination with the other credit card details, customer
> address and the service or items being purchased are going to be known to
> any number of call centre and other clerical staff across the country or
> overseas, fertile ground indeed for potential ID theft.
True, but there is a presumption that such staff will be vetted and
considered safe. Such folk may well still transgress, but it'll be more
than their job's worth if they do.
> Incidentally, there is presumably an algorithm that computes or validates
> the security digits against the card number itself, or do the merchants
> validate the details directly with their bank?
I'd guess the code is validated direct with the issuer each time.
Note that when an expired card is re-issued, it will have a different
3-digit code even when the 16-digit card number stays the same. This
means that either there cannot be such an algorithm as you suggest, or
else the code is not unique, or else (most likely) the algorithm takes
in more than just the card number. For instance, it might take in the
validity dates.
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| Re: Credit Card Security Digits [message #379950 ] |
Di, 11 April 2006 13:25 |
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> Gunslinger wrote:
> > These details in combination with the other credit card details,
customer
> > address and the service or items being purchased are going to be
> > known to any number of call centre and other clerical staff across
> > the country or overseas, fertile ground indeed for potential ID theft.
>
"Ronald Raygun" wrote
> True, but there is a presumption that such staff will be
> vetted and considered safe. Such folk may well still
> transgress, but it'll be more than their job's worth if they do.
Why? How would anyone show that it was *them*,
rather than any of the *other* "call centre and
other clerical staff across the country or overseas"?
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| Re: Credit Card Security Digits [message #379961 ] |
Di, 11 April 2006 15:08 |
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Ronald Raygun wrote:
>> The final 3 characters appearing on the reverse of the card. What is the
>> purpose of these?
>
> They are to prove that the actual card is in the shopper's possession.
> The point is that these figures are never printed on transaction
> receipts, and therefore the genre of fraud eliminated is that of
> people rummaging through bins for such receipts.
This may have been the original reason but since the full card number
isn't generally printed on receipts now (here or abroad), the ability to
determine a card number from bins is much reduced. The three digits (4
for Amex cards, conveniently printed on the front of the card for
photocopying!) are now routinely requested by all and sundry - so as to
make the system much less secure.
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| Re: Credit Card Security Digits [message #379963 ] |
Di, 11 April 2006 15:52 |
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Ronald Raygun <no.spam [at] localhost.localdomain> wrote:
> Gunslinger wrote:
>
> > The final 3 characters appearing on the reverse of the card. What is the
> > purpose of these?
>
> They are to prove that the actual card is in the shopper's possession.
> The point is that these figures are never printed on transaction
> receipts, and therefore the genre of fraud eliminated is that of
> people rummaging through bins for such receipts.
>
> > Since they are now routinely requested for postal and telephone (as well
> > as online) transactions, any value as an additional security measure is
> > (presumably) very limited.
>
> They ought to be required *only* for phone and online transactions, and
> *never* for postal ones. The whole point, surely, is that they should
> never be written down, and cannot therefore be stolen.
>
I recently received some mail which (if I had wanted to buy what they
were selling) requested the security code on the form you sent them.
It was on a corner which they promised to cut off and destroy when
they had done the card security processing but I'm not sure I'm very
keen on same.
--
Chris Green
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| Re: Credit Card Security Digits [message #379969 ] |
Di, 11 April 2006 16:36 |
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usenet [at] isbd.co.uk wrote:
> I recently received some mail which (if I had wanted to buy what they
> were selling) requested the security code on the form you sent them.
> It was on a corner which they promised to cut off and destroy when
> they had done the card security processing but I'm not sure I'm very
> keen on same.
That's outrageous. The letter could have gone "missing" in the post.
What do CC T&Cs generally say about how freely you may reveal this
code number?
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| Re: Credit Card Security Digits [message #379970 ] |
Di, 11 April 2006 16:46 |
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Tim wrote:
> "Ronald Raygun" wrote
>> True, but there is a presumption that such staff will be
>> vetted and considered safe. Such folk may well still
>> transgress, but it'll be more than their job's worth if they do.
>
> Why? How would anyone show that it was *them*,
> rather than any of the *other* "call centre and
> other clerical staff across the country or overseas"?
Well, if they use the numbers to buy stuff for themselves, they'll
be found out in the fullness of time, won't they?
If, on the other hand, they sell the numbers to others, then those
others will first need to be found, and then, I suppose, a certain
amount of torture will be required to get them to reveal their
sources.
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| Re: Credit Card Security Digits [message #379977 ] |
Mi, 12 April 2006 00:33 |
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On Tue, 11 Apr 2006 09:40:33 +0000, Gunslinger wrote:
> The final 3 characters appearing on the reverse of the card. What is the
> purpose of these?
Also, what is the purpose of the other digits back there? I've got seven
digits on my card and have never used the first four for anything.
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| Re: Credit Card Security Digits [message #379979 ] |
Mi, 12 April 2006 01:43 |
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Tom Cumming wrote:
> On Tue, 11 Apr 2006 09:40:33 +0000, Gunslinger wrote:
>
>> The final 3 characters appearing on the reverse of the card. What is the
>> purpose of these?
>
> Also, what is the purpose of the other digits back there? I've got seven
> digits on my card and have never used the first four for anything.
They're just a copy of the last four digits of the card number itself.
But why are tey there?
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| Re: Credit Card Security Digits [message #379986 ] |
Mi, 12 April 2006 09:14 |
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Ronald Raygun wrote:
>>> The final 3 characters appearing on the reverse of the card. What is the
>>> purpose of these?
>> Also, what is the purpose of the other digits back there? I've got seven
>> digits on my card and have never used the first four for anything.
>
> They're just a copy of the last four digits of the card number itself.
> But why are tey there?
A good question - perhaps to tie them to the main number?
Anyway I noticed that my new Amex cards now have the 4-digit code on the
front (I must still quote this) and the full number and an additional
3-digits on the signature strip.
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