Reject spammer

app/lib/activitypub/activity/create.rb

@@ -85,8 +85,16 @@ def process_status
     ApplicationRecord.transaction do
       @status = Status.create!(@params)
       attach_tags(@status)
+
+      # Delete status on zero follower user and nearly created account with include some replies
+      if like_a_spam?
+        @status = nil
+        raise ActiveRecord::Rollback
+      end
     end
 
+    return if @status.nil?
+
     resolve_thread(@status)
     fetch_replies(@status)
     distribute
@@ -429,4 +437,17 @@ def increment_voters_count!
     poll.reload
     retry
   end
+
+  SPAM_FILTER_MINIMUM_FOLLOWERS = ENV.fetch('SPAM_FILTER_MINIMUM_FOLLOWERS', 0).to_i
+  SPAM_FILTER_MINIMUM_CREATE_DAYS = ENV.fetch('SPAM_FILTER_MINIMUM_CREATE_DAYS', 1).to_i
+  SPAM_FILTER_MINIMUM_MENTIONS = ENV.fetch('SPAM_FILTER_MINIMUM_MENTIONS', 1).to_i
+  def like_a_spam?
+    (
+      !@status.account.local? &&
+        @status.account.followers_count <= SPAM_FILTER_MINIMUM_FOLLOWERS &&
+        @status.account.created_at > SPAM_FILTER_MINIMUM_CREATE_DAYS.day.ago &&
+        @mentions.count > SPAM_FILTER_MINIMUM_MENTIONS
+    )
+  end
+
 end