Our Access Structures service has been the target of sustained malicious activity in recent weeks. This has meant we have had to implement additional measures to try to minimise the impact of these attacks on our services. If you are inadvertently being impacted by any of these new measures, then please contact us at structures@ccdc.cam.ac.uk. We are committed to maintaining this free service for all interested communities and are currently working to ensure we can keep this service running with minimum interruption to genuine users.