Methods and systems for identifying a malfunction in the extracorporeal blood circulation of a dialysis machine are disclosed. The malfunction may be identified by detecting at least one state parameter determining a first evaluation criterion for identifying a malfunction in the extracorporeal blood circulation (FEB) using the first evaluation criterion, making a decision with respect to the presence of a malfunction in the extracorporeal blood circulation, generating a first error signal, and monitoring the detected state parameter determining at least one further evaluation criterion using the at least one further evaluation criterion, making a decision with respect to the presence of a malfunction in the extracorporeal blood circulation and generating at least one further error signal combining the first error signal and the at least one further error signal to result in a combined error signal and triggering an alarm if the combined error signal exceeds a predetermined limit value.
