The content published on web pages may be filtered by a set of different methods. These online contents are considered objectionable from the rule that blocks (filters) the content. Content Filtering applications are used by a variety of users such as companies, organizations (government and private), parents, schools, libraries and many other authority who control the access to online resources. The filtering activity can be performed at various levels of internet infrastructure: on the content provider server, ISP, corporate network or home network or end device. Usually a combination of these levels are used by different entities to perform the blocking or filtering. The term web content filtering or internet content filtering is also used to refer to filtering of contents on web sites. Various different naming for similar service exist, such as parental control, content control, online content control etc...
What is the purpose of Content Filtering?
The content generated by an online platform may be objectionable for some audience types. In a corporate environment, a company may have a standard IT practices that do not allow gambling, or adult content to be consumed by its employees. Similarly a school administration may put in place some filtering rules that will block access to some social media platforms, or sites that include violence, hate speech or gun related substances. A parent may want to protect his/her children from many contents online that may include any kind of visually disturbing content. ISPs and governments may also implement content filtering techniques to some platforms which are objectionable based on their policy or legislation.
How does Content Filtering Work?
There are various aspects of content filtering when considering how does it work? The blocking or filtering can be performed on web site contents through domain, ip address, url or within a website as item filtering. The latter one is usually called Selective Content Filtering as well. Additionally, emails can also be filtered based on the decision email servers is providing such as spam, phishing or distracting content. For the location where content filtering is performed we can classify as follows:
Server Based Filtering:
The content server may implement content filtering in order to prevent the transfer of malicious or objectionable content. Malicious or harmful content are usually found on server applications where user-generated contents are being uploaded by end users, and the server administration has to control all uploaded content against files that may include malware (malicious software), spam, scam or related software before distributing to other end users. Similarly, objectionable content are also scanned on servers depending on the policy the server implements. Another server based content filtering method is antispam and antiphishing solutions, where the emails are filtered based on their contents
Internet Service Provider (ISP) Level Filtering:
ISPs share some of the responsible for the content they are transmitting from servers to end users. Althought the responsibility is always a dispute between ISPs, servers and end users, they are usually held accountable by jurisdiction when an incident happens. ISPs can perform network level filtering since they are dealing with packets and can stop domains, urls or ip addresses. These services will also be provided as cloud based solutions and they provide dns filtering as a method of content filtering.
Network Level Content Filtering
Corporations perform content filtering on their corporate networks in order to protect their assets, reduce the bandwidth utilization and keep the productivity of their employees higher. Similarly, parents can utilize filtering tools on network devices such as ADSL or Switches that are being provided by ISPs for internet access, or can setup home firewall hardware or software to protect their children from accessing harmful content.
Content Filtering on Search Engines
Search engines such as Google, Bing or Yahoo provide capabilities to end users to filter some of the search results. This technology is called SafeSearch for all the major search engines, and provides filtering of sexually explicit contents from search results.
Content Filtering on End Device
The last location where content filtering can be implemented is on the end device, such as a PC, laptop, mobile device. There are various type of application on end devices that can filter content. These are:
Browser Extensions: A specific browser extension can block harmful content. That type of filtering will work for all browsing activities.
Native application: an application that will listen to network activities can also block traffic going in and out. This type of application usually implement an interception mechanism that listens all network related activities and block contents that are not confirming to predefined rules. This type of implementation struggle with HTTPS traffic where end-to-end encryption between server and browser is needed.
Firewall: similar to native application, firewall applications can block traffic based on ip, port and domain
Email Clients: Filtering can also be performed within an email client application in order to block malicious or spam emails.
Personal Content filtering
In the recent years, there is an increasing trend of using content filtering applications to self control or limit access to contents that may have some damage. Porn addicts is one such example where users benefit from filtering systems as a mechanism to protect themselves. Another use case is to increase productivity, and reduce the distraction that some content providers such as social media networks can generate continuously.
Types of content filtering
These type of applications may block an entire domain (such as "facebook.com") or certain urls (such as "https://www.facebook.com/groups/FirearmEnthusiasts/"), or a multimedia/document within a web page. The latter type is called Selective Content Filtering and can improve the experience of many audience by filtering only the harmful content without impacting other contents on the same domain or url. The typical use case for Selective Content Filtering is on social media platforms such as Facebook, Twitter, Snapchat where the domain or url based filtering would not be practical, but a specific disturbing content may be filtered easily and can be hidden from user visibility.
Selective Content Filtering
Selective Content Filtering is a method of selectively filtering, and blocking online contents that are offensive, explicit or objectionable within a website while allowing other non-harmful content to be loaded and displayed to the user without interference.
The typical use case for Selective Content Filtering is on social media platforms such as Facebook, Twitter, Snapchat where the domain or url based filtering would not be practical, but a specific disturbing content may be filtered easily and can be hidden from user visibility.