As soon as you open your wiki and it starts to be indexed by search engines, you will have a lot of problems.
First, spammers. These guys have long since learned to recognize even quite sophisticated captchas, which a person with the first time will not determine. In this regard, it is worth abandoning the graphics and use text captchas with an answer to the question. For example, QuestyCaptcha, which is set by default at installation and you only need to enable it in the file LocalSettings.php:
$wgCaptchaClass = ‘QuestyCaptcha’;
$wgCaptchaQuestions = array( ‘question’ , ‘answer’ $wgCaptchaQuestions = array( ‘question’ , ‘answer’ );
$wgGroupPermissions = array();
/** @cond file_level_code */
// Implicit group for all visitors
$wgGroupPermissions[‘*’][‘createaccount’] = true;
$wgGroupPermissions[‘*’][‘read’] = true;
… and so on
The easiest way is to copy this array directly to the LocalSettings.php configuration file and edit them there. I recommend that you spend a couple of hours and configure the permissions once and for all; it’s better than spending a few days fighting with spam vandals later.