blog entries for 2004/3/24

entry #1

:: Captcha Tests: Tests which are easy for humans to pass, but very hard for computers. An example:

It is hard for a computer programm to extract the letters NSF from an image of the distorted text. Current OCR (text recognition) software balks at such jobs. Thus, these simple tests can be used to block automated agents from registering for free e-mail accounts (Yahoo has been employing captcha tests for quite a while), which could then be used by spammers.

But there's a beautiful solution for the bad guys (unfortunately). And Bernhard Seefeld has it exactly right: "one has to admire the elegance and utter irony of this hack": When the automated agent is confronted with a captcha test, it posts it on a "free porn" site. Users of the site are required to pass the captcha test before they can view all the pictures. Their answers are fed back to the automated agent, which then uses them to pass the test itself.

It's funny, how computer programs can get humans to do cognitive work for them. It's almost like giving a dog a treat after he performs a trick.

More at:
Bernhard Seefeld's Blog - 21st March 04
Post-Gazette

[posted at 2004-03-24 14:06:00] TrackBack