The UK government is taking steps to discuss the role of ISP’s and their willingness to actively block minors from having online access to age-restricted content (porn sites). While this endeavor in theory, has its merits, it is not as straightforward an idea from a technical perspective. Tech News World’s Richard Adhikari explores the reality and technical limitations with industry experts: http://www.technewsworld.com/story/UK-Plan-to-Filter-Porn-Could-Be-a-Hot-Mess-Say-ISPs-71498.html
A primary limitation of any government legislation that forces ISPs to adopt protective measures will by necessity be watered down because it cannot specify the use of any particular technology due to preference and conflict of interest. Therefore, legislation will typically mandate that an ISP implement some form of protection, which will then be translated into the cheapest, best-effort service on the part of the ISP as they have no financial motivation to implement the service.
Additionally, existing techniques for protection are slow and rudimentary, making it easy for the attackers to circumvent. Image detection algorithms are extremely compute intensive, URL lists are incomplete and lack any precision on new attacks and other heuristic approaches do not work. The position of pushing responsibility to the user indicates their reluctance to address this issue for several reasons. The first, is that it is expensive to implement with no clear added revenue. The second is that they want to be agnostic for reasons of free speech and common carrier protection. The third is that there is no clear way of definitively identifying a user as an adult or a minor and any behavioral methods will have minor impact.