diff --git a/private/app_neverallows.te b/private/app_neverallows.te
index 15ab764..5e47b68 100644
--- a/private/app_neverallows.te
+++ b/private/app_neverallows.te
@@ -100,3 +100,7 @@
 
 # Do not allow untrusted apps access to preloads data files
 neverallow all_untrusted_apps preloads_data_file:file no_rw_file_perms;
+
+# Locking of files on /system could lead to denial of service attacks
+# against privileged system components
+neverallow all_untrusted_apps system_file:file lock;