Please get rid of them:
dannyboy
roger15
danielsmth15
Maybe another captcha would be in order?
Thanks,
E.
Done. Thank you very much for the hint. We are already using text-based CAPTCHA, which we (for several reasons) favor over the image-based CAPTCHA. These users anyway seem to be so-called human spam bots - and neither text-based nor image-based CAPTCHA will prevent them from spamming. Hence, we will stick to the text-based CAPTCH for usability reasons.
Alright, thanks. 