As digitization progresses, operators of energy supply networks are confronted with the IEC 61850 standard. It includes data models and communication protocols for electrical substations. Since these protocols are integral to the critical infrastructure, ensuring fault- free operation is the highest priority. In this work, the communication protocols of the standard were tested for their robustness and safety. Protocol fuzzing was used for this, a procedure in which manipulated packets are sent to a system under test in order to uncover any vulnerabilities. To do this, an original packet was captured and mutated millions of times and sent back into the network. The network was set up in a laboratory specially for these tests. It consists of three intelligent electronic devices, which represent part of a substation system. The devices were configured according to the standard. The standard-compliant functioning of the communication protocols was ensured using proprietary software. The developed fuzzing tool is based on another well-known paper. This was extended with methods of error detection and thus adapted to a black-box approach. No vulnerabilities were found in the analysed intelligent electronic devices.:Abkürzungsverzeichnis VI Abbildungsverzeichnis VIII Tabellenverzeichnis IX Listings X 1 Einleitung 1 1.1 Motivation der Norm IEC 61850 1 2 Grundlagen 3 2.1 Netzwerksicherheit 3 2.1.1 Protokoll-Fuzzing 4 2.2 Energieversorgungsnetz 5 2.2.1 Schaltanlage 6 3 Norm IEC 61850 9 3.1 Datenmodell 10 3.2 Kommunikationsdienste 12 3.2.1 Generic Object Oriented Substation Event (GOOSE) 14 3.2.2 Manufacturing Message Specification (MMS) 15 3.3 System Configuration description Language (SCL) 16 4 Stand der Foschung 17 4.1 Literaturrecherche 17 4.2 Literaturanalyse 18 5 Testanlage 21 5.1 Software 21 5.2 Aufbau 23 5.3 Konfiguration 24 5.4 Testkonzept f¨ur die Funktionspr¨ufung 25 6 Fuzzing-Test 28 6.1 Fuzzer 29 6.1.1 Repository ”61850-Fuzzing“ 29 6.1.2 Anpassung des Fuzzing-Skripts 30 6.2 Durchf¨uhrung und Auswertung 36 7 Zusammenfassung und Diskussion 39 7.1 Ausblick 40 8 Anhang 42 8.1 Teile der Norm IEC 61850 - Kommunikationsnetze und -systeme f¨ur die Automatisierung in der elektrischen Energieversorgung 42 8.2 Tabelle der Literaturanalyse 45 8.3 Listing von target alive 47 8.4 Testbericht des ’Operate‘-Befehls 48 8.5 Anlagenverzeichnis 51 Literatur 52 Eidesstattliche Erklärung 56