diff --git a/lib/travis/api/app/endpoint/authorization.rb b/lib/travis/api/app/endpoint/authorization.rb
index 122aa8e8..41b06e75 100644
--- a/lib/travis/api/app/endpoint/authorization.rb
+++ b/lib/travis/api/app/endpoint/authorization.rb
@@ -78,6 +78,7 @@ class Travis::Api::App
       #
       # * **github_token**: GitHub token for checking authorization (required)
       post '/github' do
+        check_agent
         unless params[:github_token]
           halt 422, { "error" => "Must pass 'github_token' parameter" }
         end
@@ -145,6 +146,16 @@ class Travis::Api::App
 
       private
 
+        def allowed_agents
+          @allowed_agents ||= redis.smembers('auth_agents')
+        end
+
+        def check_agent
+          return if settings.test? or allowed_agents.empty?
+          return if allowed_agents.any? { |a| request.user_agent.to_s.start_with? a }
+          halt 403, "you are currently not allowed to perform this request. please contact support@travis-ci.com."
+        end
+
         def serialize_user(user)
           rendered = Travis::Api.data(user, version: :v2)
           rendered['user'].merge('token' => user.tokens.first.try(:token).to_s)
diff --git a/lib/travis/api/app/middleware/user_agent_tracker.rb b/lib/travis/api/app/middleware/user_agent_tracker.rb
index d7d582fa..c758e0f4 100644
--- a/lib/travis/api/app/middleware/user_agent_tracker.rb
+++ b/lib/travis/api/app/middleware/user_agent_tracker.rb
@@ -37,7 +37,7 @@ class Travis::Api::App
       end
 
       def mark_travis(agent)
-        command = agent.application.comment.detect { |c| c.start_with? "command " }
+        command = agent.application.comment.detect { |c| c.start_with? "command " } if agent.application.comment
 
         if command
           mark(:cli, :version, agent.version)
diff --git a/lib/travis/api/attack.rb b/lib/travis/api/attack.rb
index 4d91ec31..dc0a247d 100644
--- a/lib/travis/api/attack.rb
+++ b/lib/travis/api/attack.rb
@@ -44,7 +44,7 @@ class Rack::Attack
   # Ban time:     5 hours
   # Ban after:    10 POST requests within five minutes to /auth/github
   blacklist('hammering /auth/github') do |request|
-     Rack::Attack::Allow2Ban.filter(request.identifier, maxretry: 10, findtime: 5.minutes, bantime: bantime(5.hours)) do
+     Rack::Attack::Allow2Ban.filter(request.identifier, maxretry: 2, findtime: 5.minutes, bantime: bantime(5.hours)) do
        request.post? and request.path == '/auth/github'
      end
   end
@@ -59,6 +59,14 @@ class Rack::Attack
      end
   end
 
+
+  ###
+  # Throttle:  unauthenticated requests to /auth/github - 1 per minute
+  # Scoped by: IP address
+  throttle('req/ip/1min', limit: 1, period: 1.minute) do |request|
+    request.ip unless request.authenticated? and request.path == '/auth/github'
+  end
+
   ###
   # Throttle:  unauthenticated requests - 500 per minute
   # Scoped by: IP address
diff --git a/lib/travis/api/v3/access_control/user.rb b/lib/travis/api/v3/access_control/user.rb
index e48bb577..5b6460fe 100644
--- a/lib/travis/api/v3/access_control/user.rb
+++ b/lib/travis/api/v3/access_control/user.rb
@@ -8,6 +8,7 @@ module Travis::API::V3
       user                = Models::User.find(user.id) if user.is_a? ::User
       @user               = user
       @access_permissions = user.permissions.where(user_id: user.id)
+      @got_request        = false
       super()
     end
 
@@ -20,6 +21,7 @@ module Travis::API::V3
     end
 
     def visible_repositories(list)
+      load_permissions
       list.where('repositories.private = false OR repositories.id IN (?)'.freeze, access_permissions.map(&:repository_id))
     end
 
@@ -47,7 +49,19 @@ module Travis::API::V3
 
     def permission?(type, id)
       id = id.id if id.is_a? ::Repository
-      access_permissions.where(type => true, :repository_id => id).any?
+
+      load_permissions if @got_request
+      @got_request = true
+
+      if access_permissions.respond_to? :where
+        access_permissions.where(type => true, :repository_id => id).any?
+      else
+        access_permissions.any? { |p| p[type] == true and p.repository_id == id }
+      end
+    end
+
+    def load_permissions
+      @access_permissions = @access_permissions.to_a
     end
   end
 end