Youssef Siher, a 30-year-old second-generation Italian researcher, was arrested on Saturday evening in Milan, accused of being the administrator of the social media channels of the 'October 17th Movement'. According to the Milan Public Prosecutor's Office, the messages disseminated online by Siher would have constituted a "continuous 'declaration of war'" aimed at generating fear among the population and destabilizing civil life. The request for validation of the arrest and pre-trial detention in prison was put forward by prosecutor Francesca Crupi and prosecutor Marcello Viola, citing the danger of flight and the repetition of the crime, as reported by RaiNews. The validation hearing is scheduled for tomorrow before the preliminary investigation judge Tiziana Landoni.

The charges contested against Siher include incitement to commit crimes with the aggravating circumstance of terrorist aims, also based on article 270 bis of the penal code, and organized violence in public demonstrations, a new crime introduced by the security decree. Milanese investigators highlight that the researcher allegedly possesses IT skills to "develop a revolutionary strategy" and that the instructions provided to users denote a "clear strategic design". Among the elements that led to the contesting of the terrorist aggravating circumstance are the reference to the 'Egyptian revolt manual' and the invitation to replicate the French situation. The 'October 17th Movement', born after the Milanese unrest, allegedly attempted to organize protests in eight cities, which were however blocked by the intervention of law enforcement.

Investigations extend to possible external connections. The Public Prosecutor's Office of Genoa is verifying links between Siher and a group arrested in December 2025 as part of an investigation into alleged funding for Hamas; however, the researcher's name does not appear in the already closed Genoese investigation. A "joining" between the movement and pro-Russian hacker groups such as "Noname" and "Dark Storm Team" is also hypothesized, with coordinated plans for cyberattacks on institutional targets on October 24th. Siher's wife, Sagia Hammoud, a 32-year-old cultural mediator, is also under investigation as co-administrator of the social media channels, but no precautionary measures have been requested for her.

Youssef Siher's profile has been described as that of a "very well-connected" and not marginalized person, with journalistic and research collaborations, as stated by Defense Minister Guido Crosetto. Interior Minister Matteo Piantedosi praised law enforcement for identifying Siher, highlighting the researcher's proximity to the "pro-Pal galaxy" and his contacts with "antagonistic circles". Siher, who has been working for an artificial intelligence startup since January, had co-authored a contribution on the 'Voice Over Foundation' with his wife, where he analyzed the 'Ramy Elgaml case' discussing systemic racism and social disparity.