Observation 1
Comparing username/firstname/lastname might not be essential. Look, an abuser is not going to use the same user name (or the real user name) twice, right?

Observation 2
Comparing passwords could score +++. The hacker might use the same password for different accounts.

Observation 3
Secret question/answer - could work if these were hand typed and not selected from a dropped-down list. Again if the answers from two accounts match, then there is a big chance that it's a duplicate.

Observation 4
Age/zipcode/dob etc are irrelevant. As the hacker will most certainly conceal his/her identity.

Observation 5
Remote host - is this an IP number? It might be a good idea to compare this if two accounts have similar/same secret answer, similar/same password. See if two accounts are from the same sub-net, etc.

Suggestions
Checkout the CPAN module String::Similarity to compare two similar strings.

Efficiency wise, this operation is at best a (O^2)/2. Most likely O^3 if you do additional table look up's. In otherwords its going to be process intensive. So it would be a good idea to buffer all the data before the compare. And try to avoid named hashes to store values, because they are relatively slow to look up. So if you want to speed up more, then use the pseudo-hashes instead.

And most of all, good luck!

In reply to Re: Identifying fraudulent users, by comparing values in database. with a hash..? by Roger
in thread Identifying fraudulent users, by comparing values in database. with a hash..? by vili

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.