spammers registering on my website

They can use human spammers

But try this new update Let me know if it stops them.

== Changelog ==

= 2.7.6 =
– (15 Dec 2012) – Tested compatible with WP 3.5
– improved spam bot detection.
– Removed CAPTCHA test pages.
– Fix possible error: preg_match() expects parameter to be string.
– Other optimizations.
– Updated Dutch language (nl_NL) – Translated by [Paul Backus](https://backups.nl/)
– Updated Italian language (it_IT) – Translated by [Gianni Diurno](https://gidibao.net/ “Gianni Diurno”)
– Added Lithuanian (lt_LT) – Translated by [Vincent G](https://www.Host1Free.com)

Still the same problem. I tried setting captcha difficulty to “hard” but no luck.

try version 2.7.6.3 and the new setting “Enable honeypot spambot trap”.

(05 Jan 2013) – added new setting “Enable honeypot spambot trap”. Enables empty field and time based token honyepot traps. For best results, do not enable unless you have a spam bot problem. Does not stop human spammers.
– fixed some bugs

let me know if it helps

I have replaced SI Captcha by another plugin that generates “x + 5 = 10” equations. That immediately solved all my problems like spam registrations and spam comments. So they were definitely not human spammers. Or they cannot solve math ??

Still like the SI Captcha method but I will reinstall and test if I have time again.

I have the same problem, but i read somewhere on the internet, there is human spammers behind another spam site, they not surfing your site, but the get the images indirectly, Human users that can post the code and return back to your site, they earn money for 1000 code for example.

Image of SI Capatcha can be accessed out side of the main site, automated spam engine have users around the world and the use one site to spam many wordpress sites.

My idea make this images can not be accessed from out side the maybe check the referral code, but that engine can emulate it also.
And check the IP of who request the image with and who request the page.