Spam Fake accounts?

I have several dolphin installs and they ALL attract extemem amounts of fake accounts advertising numerous things some which makes no since at all. These seem like mass submisions. We get hundreds in a week. If I turn up a new dolphin install its a matter of days before it happens again. Almost like something searches for dolphin installs. Does anyone have any idea what is the source of these fake accounts and how to block them? I have other social sites on the same servers and this ONLY happens to my dolphin based installs. Clues, comments, tips, ideas? Anyone?

See this post for solutions. http://www.boonex.com/forums/topic/spam-spam-spam-spam-IDEA-.htm

I don't use the captcha. I got way too many spam bots. I moved the Captcha Block to the inactive area.

I have used another human verification method for Dolphin 7.0.9 with complete success in preventing bots from joining. I learned it from a programer on the DevelopPhp web site.  In the join form create a field that has a max value of 0 (zero).  Then set the defaullt value as "Delete this text"  Your caption can also instruct the user to delete the text in the box.  For some reason bots will not complete this correctly.  You will also want a Maximum exceed error message like "You did not delete the text in this box."

I have not yet tried splitting the form into two or more pages.

There is a post with a similar spam bot solution, but I like the simplicity of this idea and it works.  So Far zero bots for me since using it about two months now. I can use auto activation too!