Strangly even image verification cannot stop some spammers There must be only two ways, either they managed to by pass the verification image or are so stupid to sit at their computer and send stupid emails to people about viagra and other rubbish things. Which one is correct? I hope the answer isn't manual verification since it would be very sad to know some people are so jobless in a part of the world that they are ready to do these types of work.
I'm guessing it would depend on how well the generated image blends in the Letters/Numbers in order for a computer to not recognize it. Yet, if someone actually does sit there and manually do all of this... then I don't know what to say about that
Ah...wow This reminds me of something.. But no need to get into that. What they do is write a type of 'super' script or whatever you may call it. That uses the same algorithm as the software you used/coded. But I doubt people even have that much time to analyze every single string and understand it's patterns...
Remember that these days, a lot of CAPTCHAs can be identified by computers. It's just a reality that AI is getting better. Also, from my understanding, there are groups of people in certain countries that will go through and answer the CAPTCHAs for practically nothing. Finally, you also have the process whereby (apparently) a site will pass a CAPTCHA image through to (for example) a free porn site and have the visitor to that site answer it for them. Then, they essentially tunnel the answer back through to your site.
CAPTCHAs may be able to decoded by computers . . . but most of the spam which is placed in forums and other locations where CAPTCHA verification is required is entered manually. I encounter it all the time from people who go through the process of registering at an anti-spam forum I run and then later posting spam. Now isn't that ironic!
Some captchas really suck too... and you can figure them out by variables in the URL or source... be careful about just grabbing any captcha script, some are not written well.