Digital technologies are actively used by terrorist organizations for recruiting supporters and planning criminal acts. At the same time, agitation, propaganda, and the transfer of criminal skills are carried out without personal contact between a representative of the terrorist organization and the future adept. One of the main forms of initiation into terrorist ideas is self-radicalization. This complicates the work of law enforcement agencies in the early identification of supporters of terrorist ideas, which necessitates monitoring activities in cyberspace, mass data collection, and their algorithmic processing. Foreign experience shows that many such activities have received their legislative consolidation, in connection with which an analysis of certain provisions of legislation in the field of countering terrorism in the UK and the USA is presented. The article emphasizes that the systematization of the huge amount of data appearing on the Internet is impossible without the creation of special programs and algorithmic processing.