http://plugins.b2evolution.net/index.php/2007/12/27/turing_test_220

Works in 2.* and I don't get comment spam. Note that if you're into trackbacks then it is NOT the weapon of choice because it does nothing there.

Are you using the antispam central blacklist system? .blogspot.com has been a keyword for a heck of a long time because of the THOUSANDS of blogspot spammers out there.

I thought there was also a captcha for v2.* but I can't find it so maybe it doesn't exist?

I have updated the anti-spam list, but I don't want to block the blogspot.com domain fully because unfortunately a lot of legitimate bloggers continue to use it.

Captha Images plugin.
http://plugins.b2evolution.net/index.php/2006/07/11/captcha_image#comments

It doesn't mark as 2.x compatible, but works well on my 2.3 system.

I was thinking more along the line of Dr.Dave's Spam Karma 2 for WordPress. Something that is transparent to the end user and works on analyzing the comment for spamminess rather than require extra inputs from the user.

I used to use SK 2 in WP and it was quite fantastic in blocking out spam.

nice thread. one question pertaining to another version for trackbacks, what type of plug in can i use for 1.10.2?

This Captha Images plugin should work in 1.10 and 2.x
http://plugins.b2evolution.net/index.php/2006/07/11/captcha_image#comments