bugtraq - Defeating audio captcha systems

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Message-ID: <478C4C1F.9070902@gmail.com>
Date: Tue, 15 Jan 2008 06:01:03 +0000
From: "José M. Palazón Romero" <josem.palazon@...il.com>
To: bugtraq@...urityfocus.com
Subject: Defeating audio captcha systems

Hi all,

Some days ago I wrote an advisory which demonstrates how the Peter's
Math Antispam Spinoff plugin for wordpress
(http://www.theblog.ca/math-anti-spam) can be defeated by its audio file.

It's hard to summarize, you better read the advisory, but in a very
small nutshell, the flaw its about not using any kind of distortion on
the audio clip, which makes it easily identificable by a script.

Here is the link:

http://docs.google.com/View?docid=df36cd52_19xzmkwqcg

I'm sure you will find the advisory inspirational, as the approach is
applicable to many other capthas, and anti-script methods.

Regards

Jose