dr. R. Holz (Ralph)

Associate Professor

About Me

I am an Associate Professor in Empirical Security Analysis and Internet Evolution in the Design and Analysis of Communication Systems Group at the University of Twente.

Before joining the University of Twente, I was Lecturer in Networks and Security at the University of Sydney (that’s Asst. Prof. in other systems), Australia. Until 2016, I was a Researcher at NICTA (later CSIRO's Data61), also in Sydney, where I worked on network security and was part of the Security Business Team.

I hold a PhD from Technical University of Munich. I did both my post-grad and under-grad studies at Eberhard Karls University, Tuebingen, one of Germany’s classic universities.

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My research interests revolve around understanding and improving the Internet for everyone, with a particular focus on security aspects. Most recently, I have been working on

  • Global-scale measurement of Internet service deployments and their security
  • Data-driven security mechanisms
  • Analysis of emerging technology and its implications

I view my work through the lens of real-world implications. The tech is not always what matters—it’s the embedding in our world that makes it meaningful. Hence, I work with other disciplines and industry alike to make the Internet a safer, more secure, and altogether more interesting and useful place.


Tarahomi, S. , Holz, R. , & Sperotto, A. (2023). Quantifying Security Risks in Cloud Infrastructures: A Data-driven Approach. In C. J. Bernardos, B. Marini, E. Rojas, F. L. Verdi, Z. Zhu, E. Oki, & H. Parzyjegla (Eds.), 2023 IEEE 9th International Conference on Network Softwarization (NetSoft) IEEE. https://doi.org/10.1109/NetSoft57336.2023.10175501
Pimienta, J., Brandt, J., Bethe, T. , Holz, R. , Continella, A., Jibb, L., & Grundy, Q. (2023). Mobile apps and children's privacy: A traffic analysis of data sharing practices among children's mobile iOS apps. Archives of disease in childhood, 108(11), 943-945. https://doi.org/10.1136/archdischild-2023-325960
Yazdani, R., Nosyk, Y. , Holz, R., Korczyński, M. , Jonker, M. , & Sperotto, A. (2023). Hazardous Echoes: The DNS Resolvers that Should Be Put on Mute. In 2023 7th Network Traffic Measurement and Analysis Conference (TMA) (pp. 1-10). IEEE. https://doi.org/10.23919/TMA58422.2023.10198955
Bertholdo, L. (2023). Anycast in the age of hypergiants: Towards tools and techniques for the other 99% of ASes. [PhD Thesis - Research UT, graduation UT, University of Twente]. University of Twente. https://doi.org/10.3990/1.9789036557320
Bertholdo, L., Ferreira, S. L. A., Ceron, J. M. , Holz, R., Granville, L. Z. , & van Rijswijk - Deij, R. M. (2022). On the Asymmetry of Internet eXchange Points - Why Should IXPs and CDNs Care? In 18th International Conference on Network and Service Management
Holz, R. , & Abhishta, A. (2021). A message from the program chairs of TAURIN 2021. In TAURIN 2021 - Proceedings of the 2021 ACM SIGCOMM Workshop on Technologies, Applications, and Uses of a Responsible Internet https://dl.acm.org/doi/proceedings/10.1145/3472951
Holz, R., Mellia, M., Bonaventure, O., Haddadi, H., Caesar, M., Gorinsky, S., Antichi, G., Camp, J., Claffy, K., Raman, B. , Sperotto, A., Vianna, A., & Uhlig, S. (2020). Update on ACM SIGCOMM CCR reviewing process: Towards a more open review process. Computer communication review, 50(3), 55-56. https://doi.org/10.1145/3411740.3411748
Choi, K. N., Kolamunna, H., Thilakarathna, K., Seneviratne, S. , Holz, R., Hassan, M., & Zomaya, A. (2020). Passive Packet Sniffing Tools for Enabling Wireless Situational Awareness. Paper presented at Cyber Defence Next Generation Technology & Science Conference 2020 (Postponed), Brisbane, Queensland, Australia.
Wan, G., Izhikevich, L., Adrian, D., Yoshioka, K. , Holz, R., Rossow, C., & Durumeric, Z. (2020). On the origin of scanning: the impact of location on Internet-wide scans. In IMC '20: Proceedings of the ACM Internet Measurement Conference (pp. 662-679). ACM SIGCOMM. https://doi.org/10.1145/3419394.3424214
Abeywardena, K., Zhao, J., Brent, L., Seneviratne, S. , & Holz, R-G. (2020). Triplet Mining-based Phishing Webpage Detection. In Local Computer Networks IEEE.

UT Research Information System

Google Scholar Link


I currently teach/co-teach:

  • Empirical Security Analysis & Engineering (Q1, 202100073) in Q1
  • Internet Security (201700074) in Q1 (from 2022)
  • Network Systems (202001025/202001150) in Q3

I am a Fellow of the UK's Higher Education Academy.

Affiliated Study Programmes


Courses Academic Year  2023/2024

Courses in the current academic year are added at the moment they are finalised in the Osiris system. Therefore it is possible that the list is not yet complete for the whole academic year.

Courses Academic Year  2022/2023

Contact Details

Visiting Address

University of Twente
Faculty of Electrical Engineering, Mathematics and Computer Science
Zilverling (building no. 11)
Hallenweg 19
7522NH  Enschede
The Netherlands

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Mailing Address

University of Twente
Faculty of Electrical Engineering, Mathematics and Computer Science
P.O. Box 217
7500 AE Enschede
The Netherlands

Additional Contact Information

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