What Is Access-Blocking? – How Is Access-Blocking Executed Against Websites?

Under Law No. 5651, access-blocking is defined as "the blocking of access utilizing domain names, IP addresses, content (URL), and similar methods." At its core, access-blocking constitutes the technical intervention by access provider ISPs—who operate the national or international internet backbone directly or through lease agreements—to restrict data traffic traversing their infrastructure, thereby preventing subscribers from reaching the blocked content. (Filtering mechanisms applied by entities that do not hold access provider status regarding their own hosted internet environments, such as individual websites, do not fall under the statutory definition of access-blocking.)

Access providers can prevent subscriber access to an online environment through numerous technical methodologies. However, Law No. 5651 explicitly stipulates that the deployed techniques must constitute domain-based, IP address-based, URL-based blocking, or derivative methods.

Access-blocking measures are fundamentally divided into two categories: ISPs may block access to an entire website or application, or they may restrict access strictly to a single piece of content or a specific portion of a website/application through a URL/content-based blocking methodology. Whole-site access-blocking can be executed at the domain level via DNS servers under the ISP's control, or at the server IP/port level via routers (since subscriber traffic traverses these routers when exiting the local area network onto the internet).

Where advanced technological infrastructure exists, ISPs can execute URL-based blocking and collateral internet filtering operations by routing traffic through proxy servers or by deploying advanced network firewall and Deep Packet Inspection (DPI) technologies. The sophistication of these technologies enables successful implementation even across encrypted architectures employing SSL or derivative protocols. However, because methodologies grounded in these high-level technologies simultaneously harbor the capability to monitor the substantive content of network traffic, their deployment for access-blocking mandates a transparent operational structure subject to strict legal oversight.