diff --git a/django/contrib/auth/backends.py b/django/contrib/auth/backends.py
index d84610ca8b..00a772fd4f 100644
--- a/django/contrib/auth/backends.py
+++ b/django/contrib/auth/backends.py
@@ -35,7 +35,7 @@ class ModelBackend(object):
         be either "group" or "user" to return permissions from
         `_get_group_permissions` or `_get_user_permissions` respectively.
         """
-        if not user_obj.is_active or obj is not None:
+        if not user_obj.is_active or user_obj.is_anonymous() or obj is not None:
             return set()
 
         perm_cache_name = '_%s_perm_cache' % from_name
@@ -63,7 +63,7 @@ class ModelBackend(object):
         return self._get_permissions(user_obj, obj, 'group')
 
     def get_all_permissions(self, user_obj, obj=None):
-        if not user_obj.is_active or obj is not None:
+        if not user_obj.is_active or user_obj.is_anonymous() or obj is not None:
             return set()
         if not hasattr(user_obj, '_perm_cache'):
             user_obj._perm_cache = self.get_user_permissions(user_obj)
diff --git a/django/contrib/auth/tests/test_auth_backends.py b/django/contrib/auth/tests/test_auth_backends.py
index 2cfcd2a097..37a93f7835 100644
--- a/django/contrib/auth/tests/test_auth_backends.py
+++ b/django/contrib/auth/tests/test_auth_backends.py
@@ -112,6 +112,33 @@ class BaseModelBackendTest(object):
         self.assertEqual(user.has_perm('auth.test'), True)
         self.assertEqual(user.get_all_permissions(), set(['auth.test']))
 
+    def test_anonymous_has_no_permissions(self):
+        """
+        #17903 -- Anonymous users shouldn't have permissions in
+        ModelBackend.get_(all|user|group)_permissions().
+        """
+        backend = ModelBackend()
+
+        user = self.UserModel._default_manager.get(pk=self.user.pk)
+        content_type = ContentType.objects.get_for_model(Group)
+        user_perm = Permission.objects.create(name='test', content_type=content_type, codename='test_user')
+        group_perm = Permission.objects.create(name='test2', content_type=content_type, codename='test_group')
+        user.user_permissions.add(user_perm)
+
+        group = Group.objects.create(name='test_group')
+        user.groups.add(group)
+        group.permissions.add(group_perm)
+
+        self.assertEqual(backend.get_all_permissions(user), set(['auth.test_user', 'auth.test_group']))
+        self.assertEqual(backend.get_user_permissions(user), set(['auth.test_user', 'auth.test_group']))
+        self.assertEqual(backend.get_group_permissions(user), set(['auth.test_group']))
+
+        user.is_anonymous = lambda: True
+
+        self.assertEqual(backend.get_all_permissions(user), set())
+        self.assertEqual(backend.get_user_permissions(user), set())
+        self.assertEqual(backend.get_group_permissions(user), set())
+
     def test_inactive_has_no_permissions(self):
         """
         #17903 -- Inactive users shouldn't have permissions in
diff --git a/docs/ref/contrib/auth.txt b/docs/ref/contrib/auth.txt
index 8509c0861a..a9f60e3234 100644
--- a/docs/ref/contrib/auth.txt
+++ b/docs/ref/contrib/auth.txt
@@ -446,26 +446,29 @@ The following backends are available in :mod:`django.contrib.auth.backends`:
         .. versionadded:: 1.8
 
         Returns the set of permission strings the ``user_obj`` has from their
-        own user permissions. Returns an empty set if the user is not
-        :meth:`active <django.contrib.auth.models.CustomUser.is_active>`.
+        own user permissions. Returns an empty set if
+        :meth:`~django.contrib.auth.models.AbstractBaseUser.is_anonymous` or
+        :attr:`~django.contrib.auth.models.CustomUser.is_active` is ``False``.
 
     .. method:: get_group_permissions(user_obj, obj=None)
 
         Returns the set of permission strings the ``user_obj`` has from the
-        permissions of the groups they belong. Returns an empty set if the user
-        is not :meth:`active <django.contrib.auth.models.CustomUser.is_active>`.
+        permissions of the groups they belong. Returns an empty set if
+        :meth:`~django.contrib.auth.models.AbstractBaseUser.is_anonymous` or
+        :attr:`~django.contrib.auth.models.CustomUser.is_active`  is ``False``.
 
     .. method:: get_all_permissions(user_obj, obj=None)
 
         Returns the set of permission strings the ``user_obj`` has, including both
-        user permissions and group permissions. Returns an empty set if the
-        user is not :meth:`active <django.contrib.auth.models.CustomUser.is_active>`.
+        user permissions and group permissions. Returns an empty set if
+        :meth:`~django.contrib.auth.models.AbstractBaseUser.is_anonymous` or
+        :attr:`~django.contrib.auth.models.CustomUser.is_active` is ``False``.
 
     .. method:: has_perm(user_obj, perm, obj=None)
 
         Uses :meth:`get_all_permissions` to check if ``user_obj`` has the
         permission string ``perm``. Returns ``False`` if the user is not
-        :meth:`~django.contrib.auth.models.CustomUser.is_active`.
+        :attr:`~django.contrib.auth.models.CustomUser.is_active`.
 
     .. method:: has_module_perms(self, user_obj, app_label)