1. ▹ Antivirus
  2. ▹ Assets
  3. ▹ Authentication
  4. ▹ Availability
  5. ▹ Basic criteria for risk analysis
  6. ▹ Computer Hacks
  7. ▹ Confidentiality
  8. ▹ Control
  9. ▹ Cryptography
  10. ▹ Cybercrime
  11. ▹ Cybercriminals
  12. ▹ DRP – Disaster Recovery Plan
  13. ▹ Data backups
  14. ▹ Data loss
  15. ▹ Defacement
  16. ▹ Disinfect machine with a live CD
  17. ▹ Disposal
  18. ▹ Email
  19. ▹ Firewall
  20. ▹ Human error
  21. ▹ IDS/IPS
  22. ▹ Image rights
  23. ▹ Impact
  24. ▹ Integrity
  25. ▹ Internet and copyright
  26. ▹ Legal Aspects
  27. ▹ LuxTrust
  28. ▹ Malicious Codes
  29. ▹ Malicious websites
  30. ▹ Network segmentation
  31. ▹ Password
  32. ▹ Patches
  33. ▹ Phishing
  34. ▹ Physical faults
  35. ▹ Securing a fixed workstation
  36. ▹ Physical theft
  37. ▹ Recommendations for securing a file server
  38. ▹ Recommendations to secure a server connected to Internet
  39. ▹ Recommendations to secure a Web server
  40. ▹ Removable devices
  41. ▹ Risk processing
  42. ▹ Spam – unwanted emails
  43. ▹ SSL/TLS – encryption technologies on the web
  44. ▹ Update softwares with Secunia PSI
  45. ▹ Security Charter
  46. ▹ Social engineering
  47. ▹ Threat
  48. ▹ Virtual Private Networks (VPNs)
  49. ▹ Vulnerabilities
  50. ▹ Web of Trust - WOT
  51. ▹ Web filter – Proxy
  52. ▹ Why is it important to protect your computer?

Web filter – Proxy

In brief

A large number of websites, both legal and illegal, that can be freely accessed online have content that is malicious, inappropriate, prohibited or bad for productivity. Accessing malicious websites may result in the installation of malicious codes without the user’s knowledge. The organisation may also be held liable for access to prohibited or illegal content.

To prevent employees accessing such websites, the organisation can install a web filter as a means of protection.

In technical terms, these filters are called “web proxies” and can take several forms. The best-known free proxies are “squid and squidguard”, “DansGuardian” and “HAVP”, which can be found in a large number of free or paid firewall products.

How it works

A web filter analyses all communications (content and/or recipients) to and from the Internet to detect exchanges with sites hosting malicious, inappropriate or prohibited content. This filter is not to be confused with the browser’s phishing filter, because unlike the latter, which is installed in the user’s browser, the web filter runs on a dedicated server and cannot be easily circumnavigated by the user.

URL analysis

A web filter that analyses URLs has a database that links URLs with content categories. These databases are managed by specialised companies who associate the websites with various categories, such as pornography, gaming, gambling, and so on.

Once a new website has been discovered, it is categorised and, if necessary, added to the database. This type of filter does not prevent access to brand new websites that haven’t yet been categorised or access to websites that have only recently become malicious.

The organisation can nevertheless filter different content categories, such as pornography, gambling, social networks, etc.

Content analysis

Some web filters are able to analyse the content of a website a user wants to visit. Based on a list of key words, the filter allocates a category to the websites visited and either displays or doesn’t display the requested content. This filter is useful for preventing access to recent content for which the URL analysis wouldn’t have worked, but can also generate a lot of false positives.

Malicious content analysis

Some filters contain antivirus programs and can analyse the content of websites visited and block access to potentially malicious software.

Image analysis

Some web filters can analyse the requested images. The filter selects the images on the website visited and allocates them to a category before displaying or not displaying the content.

Security policy

Draw up and enforce the following sectoral policies:

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