A DDoS attack targeted the General Council of the Judiciary's (GCJ) website, poderjudicial.es, which includes a subsection for the Supreme Court, the court said.
The website is currently operating normally.
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The Supreme Court is supposed to hear cases of 12 of 18 politicians, while the remaining six cases will be sent to the High Court of Justice of Catalonia. Those 12 cases include ones for former Vice President and leader of the Republican Left of Catalonia political party Oriol Junqueras, Speaker of the Catalan Parliament Carme Forcadell, and political activists Jordi Sanchez and Jordi Cuixart.
When the new Catalan government led by President Quim Torra came to power in June, Madrid restored the region's autonomy.