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Blocklist Subscriptions for Guardian Products
In order to ensure that a Guardian Web Content Filtering solution operates at maximum effectiveness it is essential that the blocklists are kept up-to-date. Guardian blocklists are automatically updated on a daily basis and comprise the following five elements:
- Dynamic Content Rules
- URL, Domain and IP Address blocklists (categorized, e.g. pornography, news, sport etc.)
- Internet Watch Foundation supplied CAIC (Child Abusive Images and Content) blocklists
- Malicious Code Detection Signatures (e.g. browser exploits, ActiveX, Java Applets and scripts)
- File (MIME) type and extensions list
Dynamic Content Rules are used by the content inspection engine that lies at the heart of Guardian, screening the actual content, context and construction of web pages, so that objectionable, hidden and malicious material (including anonymous proxies) can be accurately identified and blocked. These rules are regularly revised and extended, with the addition of many new aspects as the web evolves. Out-of-date dynamic content rules may result in under or over blocking.
These are generally described as the URL blocklist, used by Guardian to identify known objectionable sites (eg playboy.com) and time-wasting sites (such as facebook and ebay). These lists contain millions of references and are constantly being refined and extended, both by the addition of new entries and new categories.
Guardian includes the ability to detect malicious code embedded within web pages. This has become a common technique to plant Spyware, viruses and Trojans on a user's computer, using in-page executable code like Active-X controls, Java Applets and Scripts. Such in-page exploits are not recognized by traditional anti-virus software. Like anti-virus signatures that have to be updated regularly to stay abreast of the latest virus threats, Guardian's Malicious Code Detection Signatures also need to be kept up-to-date to maintain maximum effectiveness.
This section of the blocklist contains information on known dangerous and non work-related file types, such as executable, music and video files. Every file can be identified from its MIME type property, allowing Guardian to block the download of music, video and executable files from web sites. This is a far more reliable technique than checking the file extension which is often forged to disguise dangerous files containing Spyware or Trojan Horse programs. Guardian can also be configured to block ZIP archives which may contain hidden executable programs.
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