Content filter
A content filter (from English content "content") is a program that is used to filter certain undesired content (e.g. data , images , audio files , ...) before it can get from one network to another.
That is why a content filter is usually located at the interface to the entrance of the network and controls the data coming into the network before it can reach the network part accessible to the users.
These content filters are often used by companies , governments and organizations to identify certain content according to its characteristics and properties . So that this recognized content can be blocked and excluded from your own network. The aim is to protect the users of a network from dangerous (e.g. terrorism - propaganda ) and illegal content (e.g. copyright infringement ). The productivity of employees can also be improved (e.g. less distraction ) or the technical security of a network can be increased (e.g. against industrial espionage ).
An example of how governments use content filtering is blocking illegal, offensive, or harmful websites .
Features and functions
A filter that can be set in detail makes it easier to control the content viewed. Sometimes unnoticed by the user, this system blocks or filters, for example, websites or e-mails with regard to individual words, typical phrases, images or links. Content filters are part of the BSI recommendations for the operation of secure mail servers.
Most of these areas are configured by means of a categorization. Lists ( databases ) are used, such as the negative blacklist or a whitelist that allows access anyway. Typical examples of predefined categories are pornography or right-wing extremism .
Simple content filters
Simple filters only check the occurrence of certain selection criteria. The disadvantage of using very simple filters is that each page is blocked with corresponding words. Pages that use blocked words in a different context can also be blocked. If, for example, the word “sex” is blocked in any form, not only is every page that contains this word - also in harmless context - used in general, but also the page for the village of Sexten or the Wikipedia entries right-wing extremism and random experiments . This is also known as the Scunthorpe problem .
Another simple method is to block certain ports or network protocols.
Intelligent content filters
In order to avoid the disadvantages of simple methods, intelligent filters work with weights and only reject a page if a certain relevance is exceeded. They also use heuristic procedures and greylists for e-mails .
In contrast to a URL filter with a high probability of being hit, an intelligent content filter is able to correctly assess websites or e-mails. Also can be used for good for a certain time befundene URLs cached are to the time-consuming testing to avoid Repeated request.
restrictions
Simple filters can only check URLs , texts and images that are classified according to certain standards. Texts that are displayed in image form can only be checked if the filter also supports OCR text recognition . Of course, it is only possible to keep blacklists of all unwanted pages to a limited extent.
Advanced systems also combine antivirus program with the content filter to here about smuggled malware , for example, via scripts or images on the client will get to realize.
Today (2014) content filters are often offered as a separate service for a fee, the service providers take over the updating of the filter lists and the intelligent filtering according to configurable criteria. There are considerable costs per year and per Internet user.
See also
Individual evidence
- ↑ Contentfilter :: CF (content filter) :: ITWissen.info. Retrieved March 14, 2020 .
- ↑ mattpennathe3rd: content filtering . Retrieved on March 14, 2020 (German).
- ↑ Social networks: companies lock Facebook out . In: FAZ.NET . ISSN 0174-4909 ( faz.net [accessed March 14, 2020]).
- ↑ heise online: Family Minister: Providers take part in blocking child porn. Retrieved March 14, 2020 .
- ↑ ISi-Check - Secure operation of e-mail servers . (PDF) BSI, accessed on: November 13, 2014
- ↑ Michael Whitman, Herbert Mattord: Principles of Information Security . Cengage Learning, January 1, 2011, ISBN 1-111-13821-4 , p. 277.