On 19 October 2016, the European Court of Justice (ECJ) held (Case C-582/14 – Breyer v Federal Republic of Germany) that dynamic IP addresses may constitute personal data. The ECJ also held that a website operator may collect and process IP addresses for the purpose of protecting itself against cyberattacks, because in the view of the Court, preventing cyberattacks may be a legitimate interest of a website operator in its effort to continue the operability of its website.

The ECJ’s ruling was based on two questions referred to it by the German Federal Court of Justice (BGH). In the underlying German proceedings, a member of the German Pirate Party challenged the German Federal Government’s logging and subsequent use of his dynamic Internet Protocol (IP) address when visiting their websites. While the government is a public authority, the case was argued on the basis of German provisions that address both public and private website operators, and is therefore directly relevant for commercial companies.

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