OK so it’s confirmed : captcha is no longer a foolproof method to avoid spammers.
Although not all captchas can be circumvented with software, many does.
Thanks to Sam who has informed us that this is the case.
btw; regarding complaints that captcha is alienating disabled visitors, there’s a workaround – provide a link which will play an audio, which tells the alphabets in the captcha. However, this is not very easy to implement indeed at the moment.