Recently I am receiving some user registration Spams...I use reCaptcha module but I want to add a anti-spam questions while User registers registration as you see in many forum sites.
Does anybody know how to do that ?...is there any module ..?
You can also customize captcha by the CAPTCHA Pack module. Here is a quote about it (from the module's project page):
... contains several CAPTCHA types for use with the CAPTCHA module. The CAPTCHA Pack module is meant to provide lightweight, yet effective alternatives for the traditional image CAPTCHA, which is undesirable in certain situation (e.g. bandwidth restrictions, cpu restrictions, accessibility constraints, etc).
You are probably looking for http://drupal.org/project/textcaptcha but if you have human spammers, they can answer any of these questions just as easily as completing a reCaptcha.
I have found the best way is to ask a question as part of your Captcha. Either of these should work:
https://www.drupal.org/project/captcha_questions
https://www.drupal.org/project/riddler
The way you foil spambots is to ask a specific type of question that can't be solved by a Google search. If a Google search can solve your question, then a spambot will defeat it.
For example, I ask the user to select a word that doesn't fit in the pattern, such as "Which word doesn't belong? Washer, Dryer, Pony, Stove, Refrigerator."
I make it obvious for humans. I don't use any terms that could be a possible answer.
You can't stop human spammers, and that's not the intent, because you are then stopping humans. You are stopping spambots.
Human spammers reveal themselves, and you get rid of them and their content quickly.
I use this on a forum and a site, and so far zero spambots have been able to register or send me a spam e-mail. Zero. On my site, I have had 560 failed attempts and zero successful attempts to register. The first link has a tool that lets you see the failed attempts.