Article 15 prevents Member States from imposing on internet intermediaries, with respect to activities covered by Articles 12-14, a general obligation to monitor the information which they transmit or store or a general obligation to actively seek out facts or circumstances indicating illegal activities. This is important, as general monitoring of millions of sites and web pages would, in practical terms, be impossible and would result in disproportionate burdens on intermediaries and higher costs of access to basic services for users. [73] However, Article 15 does not prevent public authorities in the Member States from imposing a monitoring obliga tion in a specific, clearly defined individual case.[73] In this context, it is important to note that the reports and studies on the effectiveness of blocking and filtering applications appear to indicate that there is not yet any technology which could not be circumvented and provide full effectiveness in blocking or filtering illegal and harmful information whilst at the same time avoiding blocking entirely legal information resulting in violations of freedom of speech.