Guide to ISP filters and web blocking

A recent Ofcom report shows children may be too trusting of online content, with more than a quarter of respondents between the ages of 8 and 15, mistakenly believing Google’s top search results were specifically selected by figures of authority.

For parents, educators, and government officials alike, these findings are a cause for concern.

While the Internet’s fluidity and the abundance of content have made it a rich trove of information, long-held concerns about credibility, malicious content and cyber-bullying, still remain.

Government action

As fake news, click-bait and hate speech grows in prevalence online, governments are working to find ways to protect families from content deemed too sexually explicit, violent, or dangerous.

For its part, the UK government has pushed Internet Service Providers (ISPs) to enable web-filtering of dangerous or malicious content online. Working with providers, the government announced that family-friendly network level filtering would be available to all new and existing broadband customers by 2014. Anyone subscribing to a broadband service now will find that the filters are automatically enabled.

But how does this impact Internet subscribers? What are web filters? And how do they work?

What are ISP web filters?

Web-filtering or web-blocking involves the restriction or control of content that Internet users are able to access via their ISP.

The family-friendly network level filters brought in by many broadband providers mean that UK Internet subscribers are prohibited from accessing a range of websites by default, specifically adult or illegal content.

What websites are blocked by these filters?

The filters are based both on lists of blacklisted or restricted websites and through an automatic scan of keywords to determine whether a site should be filtered.

The majority of categories filtered are related to violence, obscenities, or nudity. However, ISPs also work to block websites that contain malware or attempt to “phish” sensitive information like usernames, passwords, or credit card details.

Filtering consistency among ISPs is sparse, as each has its own way of categorizing and filtering content. To find out if a website is filtered, you can use web tools like, from the Open Rights Group.

How can you change or update your web-filtering settings?

For most ISPs, web-filtering occurs automatically. Internet subscribers wanting to access blocked content can choose to ‘opt-out’ of the network level filters by logging into their ISP account controls.

What’s important to remember is that these filters exist at the network level, meaning that even with customization, all users within a household are subject to the same web filters. This is great for parents, who do not need to worry about what device kids are using to access the internet, but it can be restrictive for the adults and older children in the household.

Instead of a full on opt-out, other options do exist. Internet subscribers can customise their filters to their needs, avoiding feverish web-blocking, but maintaining some form of controls. ISPs provide features like timer, homework mode, category controls, or blacklisting and whitelisting, which allow subscribers to select time slots, categories, or selective websites they opt to filter the content of.

In partnership with