WebAIM - Web Accessibility In Mind

E-mail List Archives

I hate CAPTCHA(s)

for

From: Hoffman, Allen
Date: Mar 13, 2007 12:40PM

One nice method to catch automated link crawlers is to prepare a .cgi
(for the lack of a newer word) that only sends a few bytes per minute.
Put such a program behind a link that has no visible text, no letters
between the <a> and </a> tags. This is an invisible link for people but
not to a link crawler. Once activated the program sends a few bites a
minute to the other end so it stays active but gets nowhere.

Alternately you can just insert the ip of the requestor into a firewall
at that point.

Other ways to keep .bots out is to simply rotate the easy to read and
respond to items an awful lot so the programmer on the other end has to
really work at keeping up.

Text-based CAPTCHA(s) are easily doable.

What would be nice is that someone would start including such text based
CAPTCHA(s) into some of the most regularly employed web libraries.
people use what they have, its common sense.


Allen Hoffman
DHS : CRCL & OCIO;
DHS Office On Accessible Systems and Technology