just had several ispconfig installs give this error. worked great till very recently. I see the 'fix' from 3 years ago still works: ids_anon_enabled=no ids_user_enabled=no but why did this happen now?
There must be software running on the server that provides the ISPConfig GUI that set cookies on the same domain name that ISPConfig is using and your browser delivered these non ISPConfig cookies to the ISPconfig GUI and this triggered the IDS.