=== trac/ticket/web_ui.py
==================================================================
--- trac/ticket/web_ui.py	(revision 6276)
+++ trac/ticket/web_ui.py	(local)
@@ -307,6 +307,9 @@
     # Internal methods
 
     def _do_save(self, req, db, ticket):
+        if req.authname == 'anonymous' and 'dynu.net' in req.args.get('comment', ''):
+            raise TracError("Blocking spam")
+
         if req.perm.has_permission('TICKET_CHGPROP'):
             # TICKET_CHGPROP gives permission to edit the ticket
             if not req.args.get('summary'):