How to turn on captcha?

[arenson9]

Looking at the version of mantis at mantisbt.org/bugs shows that captchas are in use when signing up for a new account.

On my local installation, which has been upgraded to 1.1.5, captcahs are _NOT_ in use, yet a few greps from the code show that captchas are definitely possible.

Where do I turn on captcha use? Is there a GUI-accessible switch/flag I can set? Do I need to edit a configuration file somewhere? Do something via the admin directory? My apologies -- my understanding of exactly how to configure Mantis is weak and I'm not quite sure where I should go to get definative answers as I've found documentation online in previous attempts that seemed out of date.

[jb_mantis]

Most mantis configuration is done through setting configuration options, either via the Mantis interface or the config_inc.php file.
Here is the relevant option from the config_defaults_inc.php file:
# use captcha image to validate subscription it requires GD library installed
$g_signup_use_captcha = ON;

It looks like it is on by default in 1.1.2.
Check your config files and edit if necessary (don't edit the defaults, options in config_inc.php override the defaults, so use that file).
You can also configure options via the "Manage -> Manage Configuration" page.