Spam blacklist stored in spammers.txt can't be disabled by any configuration parameters nor this functionality is not mentioned anywhere in administration section. I spent couple of hours with finding why my properly bought ads are not counted in Matomo statistics!

Solution is simple. Replace core/Tracker/VisitExcluded.php code:

if (!$excluded) { $excluded = $this->isReferrerSpamExcluded(); if ($excluded) { Common::printDebug("Referrer URL is blacklisted as spam."); } }

with:

$generalConfig = Config::getInstance()->General; if (!$generalConfig['disable_spam_excluding']) { if (!$excluded) { $excluded = $this->isReferrerSpamExcluded(); if ($excluded) { Common::printDebug("Referrer URL is blacklisted as spam."); } } } else Common::printDebug("Spam blacklist is disabled.");

(and of course add use Piwik\Config; to import definition).