Data retention is being in detail described by the European Directive 2006/24. Data retention ED requires:
- specific traffic data to be retained so that these can be made available to competent authorities for the "detection, investigation and prosecution of serious crime",
- the retention of large quantities of personal data for periods longer than needed for commercial purposes. These data are capable of revealing significant information about a person's private life. Accordingly considerable harm could be done to personal integrity if these data were to leak to or be accessed by unauthorised persons.
Article 4 defines the quality of the data that an Operator must retain. Namely, an Operator must retain the Calling telephone number, the Name and the Address of the Subscriber, the Telephone Number(s) Called, the Telephone Number(s) to which the call is routed (to cover cases like call diversion, one-phone and free-phone services), the Name and Address of the Called Subscriber, the Date and Time of the Start and End of the Call and the Telephone Service Used.
Finally, Article 6 tries to define in a most flexible way the period for which the Operations need to retain the previously mentioned information. Article 6, therefore, states that the retention period should be no less than 6 months and no more than two years.