Autoban dmail spambots (#3408).

If a user sends spam to more than 10 users within a 24 hour window,
automatically ban them for 3 days.

app/models/dmail.rb

@@ -1,6 +1,11 @@
 require 'digest/sha1'
 
 class Dmail < ApplicationRecord
+  # if a person sends spam to more than 10 users within a 24 hour window, automatically ban them for 3 days.
+  AUTOBAN_THRESHOLD = 10
+  AUTOBAN_WINDOW = 24.hours
+  AUTOBAN_DURATION = 3
+
   include Rakismet::Model
 
   with_options on: :create do
@@ -23,6 +28,23 @@ class Dmail < ApplicationRecord
   rakismet_attrs author: :from_name, author_email: :from_email, content: :title_and_body, user_ip: :creator_ip_addr_str
 
   concerning :SpamMethods do
+    class_methods do
+      def is_spammer?(user)
+        return false if user.is_gold?
+
+        spammed_users = sent_by(user).where(is_spam: true).where("created_at > ?", AUTOBAN_WINDOW.ago).distinct.count(:to_id)
+        spammed_users >= AUTOBAN_THRESHOLD
+      end
+
+      def ban_spammer(spammer)
+        spammer.bans.create! do |ban|
+          ban.banner = User.system
+          ban.reason = "Spambot."
+          ban.duration = AUTOBAN_DURATION
+        end
+      end
+    end
+
     def title_and_body
       "#{title}\n\n#{body}"
     end
@@ -80,6 +102,8 @@ class Dmail < ApplicationRecord
           copy.owner_id = copy.from_id
           copy.is_read = true
           copy.save
+
+          Dmail.ban_spammer(copy.from) if Dmail.is_spammer?(copy.from)
         end
 
         copy
@@ -119,6 +143,10 @@ class Dmail < ApplicationRecord
   end
   
   module SearchMethods
+    def sent_by(user)
+      where("dmails.from_id = ? AND dmails.owner_id != ?", user.id, user.id)
+    end
+
     def active
       where("is_deleted = ?", false)
     end

test/unit/dmail_test.rb

@@ -3,6 +3,7 @@ require 'test_helper'
 class DmailTest < ActiveSupport::TestCase
   context "A dmail" do
     setup do
+      User.any_instance.stubs(:validate_sock_puppets).returns(true)
       @user = FactoryGirl.create(:user)
       CurrentUser.user = @user
       CurrentUser.ip_addr = "1.2.3.4"
@@ -27,6 +28,20 @@ class DmailTest < ActiveSupport::TestCase
           assert(@recipient.dmails.last.is_spam?)
         end
       end
+
+      should "autoban spammers after sending spam to N distinct users" do
+        Dmail.any_instance.expects(:spam?).returns(true)
+
+        users = FactoryGirl.create_list(:user, Dmail::AUTOBAN_THRESHOLD)
+        users.each do |user|
+          Dmail.create_split(from: @user, to: user, title: "spam", body: "wonderful spam")
+        end
+
+        assert_equal(true, Dmail.is_spammer?(@user))
+        assert_equal(true, @user.reload.is_banned)
+        assert_equal(1, @user.bans.count)
+        assert_match(/Spambot./, @user.bans.last.reason)
+      end
     end
 
     context "filter" do