Re: [ISN] Computer-savvy crooks steal cards, charge up

From: mea culpa (jerichoat_private)
Date: Tue Aug 18 1998 - 21:11:33 PDT

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    Forwarded From: John Q Public <tpublicat_private>
    |WASHINGTON (AP) -- High-tech thieves rang up international charges of
    |almost $1 million on the debit cards of members of a Washington-area
    |credit union by using computers to guess account numbers, The Washington
    |Post reported today. 
    |Sophisticated computer programs apparently analyzed sample credit card
    |numbers, then generated ones that turned out to be valid about half the
    |time, said Mark Cis, vice president of corporate property and casualty for
    |CUMIS Insurance Society, a credit union insurer that has investigated the
    I remember hearing about this approximately 9 months ago when a bunch of
    people got busted in Colorado.  I thought the report said this started in
    Durango, Colorado, but that's a little bitty town in southwest BFE.  Just
    because they were the first to get busted doesn't mean it came from there,
    however Colorado banks were the first I heard to reissue their VISA debit
    The scheme is: you take two cards from one bank and effectively divide the
    difference between the issued numbers.  The chances were very high that
    some of the numbers were valid.  If you had two 'in sequence' it was
    simple to determine the next and previous issued numbers as they were
    'sequential' with the common difference. 
    Simply, if we knew card #4 and card #16 worked, you're looking at possibly
    card #10 (difference between 16 and 4, divided by 2).  If #8 and #12
    worked instead, you were looking at the difference divided by 3.  Once you
    know the pattern between your known range, going out of those boundaries
    were exceptionally likely.  Thus the reasoning for issuing cards with not
    much in common with each other.  Most banks issued this way because it was
    a quick way to allocate a lot of cards without using a large span of
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