Bots are often programmed to defeat the most popular validation methods, such as phpBB's graphical validator, but even a simple custom validation will defeat virtually all of them. I just use a randomly generated 6-character hex string that people have to fill in at the bottom of the form, and since I started doing that, I've gone from hundreds of spams to only a single spam submission - and even that one may have been put through by a human.

The problem with graphics is that a sufficiently obfuscated graphic is also hard for people to see, and if the graphic doesn't load, people can't submit the form. Text is easier to defeat, but anyone who's spending that much effort to defeat your site security specifically can probably come up with much nastier ways to mess with you. Email bombing, or loading your most processor-intensive page hundreds of times per second, etc. Your security only needs to be good enough to stop the usual stupid, impersonal spam bot, but not so good that it irritates your users.

In reply to Re: newb: Best way to protect CGI from non-form invocation? by TedPride
in thread newb: Best way to protect CGI from non-form invocation? by JCHallgren

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.