Earlier this month, Mollom was officially discontinued. If you still have the Mollom module installed on some of your Drupal sites, form submissions that were previously protected by Mollom will behave as if Mollom was offline completely, meaning any spam Mollom would've prevented will be passed through.

For many Drupal sites, especially smaller sites that deal mostly with bot spam, there are a number of great modules that will help prevent 90% or more of all spam submissions, for example: