‘Cyber Due Diligence’: A Patchwork of Protective Obligations in International Law

Photo by Kevin Ku

With a long history in international law, the concept of due diligence has recently gained traction in the cyber context, as a promising avenue to hold states accountable for harmful cyber operations originating from, or transiting through, their territory, in the absence of attribution.

Nonetheless, confusion surrounds the nature, content, and scope of due diligence. It remains unclear whether it is a general principle of international law, a self-standing obligation, or a standard of conduct, and whether there is a specific rule requiring diligent behaviour in cyberspace.

This has created an ‘all-or-nothing’ discourse: either states have agreed to a rule or principle of ‘cyber due diligence’, or no obligation to behave diligently would exist in cyberspace.

In their new article in the European Journal of International Law, Dr. Antonio Coco, Lecturer in Law at the University of Essex, and Dr. Talita de Souza Dias, Postdoctoral Research Fellow at the Oxford Institute for Ethics, Law and Armed Conflict (ELAC), propose to shift the debate from label to substance, asking whether states have duties to protect other states and individuals from cyber harms.

By revisiting traditional cases, as well as surveying recent state practice, the authors contend that – whether or not there is consensus on ‘cyber due diligence’ – a patchwork of different protective obligations already applies, by default, in cyberspace.

At their core is a flexible standard of diligent behaviour requiring states to take reasonable steps to prevent, halt and/or redress a range of online harms.

A copy of the authors’ article can be accessed here.


This is an Open Access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted reuse, distribution, and reproduction in any medium provided the original work is properly cited.

Article full citation: Antonio Coco, Talita de Souza Dias, ‘Cyber Due Diligence’: A Patchwork of Protective Obligations in International Law, European Journal of International Law, Volume 32, Issue 3, August 2021, Pages 771–806, https://doi.org/10.1093/ejil/chab056.

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