added a lock icon

app/controllers/user_controller.rb

@@ -50,10 +50,10 @@ class UserController < ApplicationController
   def groups
     @user = User.where('LOWER(screen_name) = ?', params[:username].downcase).first!
     @groups = if current_user == @user
-                @user.groups.all
+                @user.groups
               else
-                @user.groups.where(private: false).all
-              end
+                @user.groups.where(private: false)
+              end.all
   end
   # endregion
 

app/views/user/groups.html.haml

@@ -9,6 +9,9 @@
 
     %ul
       - @groups.each do |group|
-        %li= group.title
+        %li
+          - if group.private?
+            %i.fa.fa-lock
+          = group.display_name
 
   .visible-xs= render 'shared/links'