How to prevent comment posting when it has specific words in it? I´ve searched for all Drupal 7 modules that try to give some SPAM protection, but haven´t found what I need, maybe I´ve overlooked something?

I need to prevent anonymous comment posting when comment has specific -configurable- spammy words. How may I do that?
You can try Spam module.

It runs filters on posted content, for example using regexps.

Another way is to write a Rule that examines posted comments and deny them if certain words are found, but unfortunately this module is only available for Drupal 6.

And also you can write a validate function to the comment form, examine the content on submission and use form_set_error if you detect those words. To do this just implemente the hook_form_alter (or the hook form alter with form id), add your valditation function:

$form['#validate'][] = 'you_custom_validate_function';