The measure of collecting information from electronic communications service providers helps to remove the diffi culties encountered by the authorities in exercising their tasks of preventing and combating organized crime, terrorism or other serious crimes. The use of electronic transfers, free access to the Internet and super-sophisticated communication technology allow criminal structures to intensify the commission of crimes with unidentifi ed perpetrators, thus eroding the authority of states. Traffi c data facilitates the identifi cation of the subscriber or user of the service, allowing the competent state bodies to act effectively to prevent, identify and investigate serious crimes. Cybercrime experts estimate that traffi c data in the virtual world is the equivalent of fi ngerprints taken during on-site research. Given that data retention is an interference with the right to privacy, it is necessary to ensure compliance with the necessary and proportionate nature of the interference with the aim pursued (prevention, detection and investigation of serious crimes, defense of public order and national security) by providing limited categories of data that can be retained and the fact that the measure does not refer to the content of this data.