A look at Internet Filtering Technologies

presented by Cynthia Beuselinck
at the Odyssey '98 Conference
Calgary, AB, Canada
March 14, 1998

Welcome. Your attendance here today attests to the fact that filtering Internet access is an issue that continues to confront educational environments. This session isn’t about whether we should or should not use Internet filtering technologies - those are decisions that can only be made after considering numerous variables within your specific environment, and even then with the understanding that whatever you decide you will be challenged. This session also is not about filtering products. In the real-time world of the Internet, products appear and evolve daily.

What we are going to discuss is how filtering technologies work. We’re going to look at what types of filtering are available, the methods they use to filter, and some points to consider in your decision process. It is my hope today to equip you with a knowledge base that can assist you through the mine field of Internet filtering products, services and issues.

I will begin by saying that no Internet filtering system is a 100% guarantee that inappropriate information will not reach a desktop. Let’s not go in blindfolded here. There is simply no solution that will ever replace human supervision and sound guidance. Any filtering technology being considered should be viewed as an additional component that backs up a local Accepted Use Policy (AUP) document. Internet filtering technology is a method of reducing the risk; it cannot eliminate it.

That having been said, let’s look at how it works.

There are currently two types of Internet filtering in use. Hardware filtering or software filtering; everything else is some combination of these two. Hardware filtering utilizes configurations done to physical equipment to block very specific information from traveling through it. Usually it is employed as a security measure rather than a "filter" since blocks must be put in manually, are absolute until changed, and usually require a technician to configure each time.

Software filtering comes in two flavors: client side and server side. Client side means that the software is loaded in individual workstations and any configuration or updates must be done to each station. Client side filtering is usually less expensive and is easy to install since it is just another piece of software loaded onto the computer. However, it is also high maintenance and not very secure since it is resident on the workstation itself and is fairly easily tampered with. Some client side software can be loaded on a server which is one way to lessen the maintenance and increase security, but a better solution would be to progress to a server side software as it is designed for such an environment.

Server side software functions at a remote location from the user. This allows a single configuration and a central point for updates allowing for much simplified maintenance and administration. It is also more secure as it is not resident on the local machine making it unlikely that users can tamper with it. A special type of server side filtering which is gaining popularity is a filtering subscription service. They generally use both hardware and software in the process and provide a number of other beneficial services. By means of a proxy server, options such as caching of visited sites and a variety of usage reports are often included. The caching of sites can substantially increase efficiency of network resources and reporting allows administration to monitor their Internet activity.

Both client side and server side filtering use a variety of methods to filter the information coming through it. No one method is perfect in itself, but will be used in varying degrees depending on the filtering software itself this is where you have to do your homework about the product you are considering. What methods the software uses and how much it can be configured to suit you are what determine how useful it will actually be in your situation. A properly selected filtering product will be effective, flexible and virtually transparent; one where care has not been taken to match your needs will cause constant frustration.

Internet Rating systems

The W3C has been working for some time on a standardized rating system that embeds digitally signed labels into documents according to a very specific rating scheme. Known as the Platform for Internet Content Selection (PICS), it is an official W3C recommendation. The ratings would be read by web browsers and the delivery of the information would be dependent on how a user has set up the browser to receive rated pages (a current example is the Content Advisor in newer versions of Internet Explorer). For further information, refer to the W3C site at http://www.w3.org. Other rating systems are also under review, but W3C holds an enormous influence in setting standards on the Web.

Internet Keyword blocking

The oldest and least useful of the filtering methods, keyword blocking employs a predefined list of "inappropriate" words. When Internet content is requested, the software automatically scans the documents for any of the offending words and will block documents in which they are found.

Internet Protocol blocking

A very broad based blocking method that disables access to entire protocols (all of IRC, all newsgroups, etc.). It is most effective as a method of managing resource allocation rather than filtering.

Internet Host blocking

Blocks entire hosts, or sometimes specific pages on a host. Intellectual decisions to deselect sites are made by individuals examining each one using a specific set of criteria for exclusion. The list of URLs is usually resident in a database accessed by the software each time Internet content is requested sites found in the database are blocked.

Characterized Content Rating

A community of human raters is used to rate sites and add them to a database that is accessed by a specific search engine. Rather than block access, characterized content rating simply provides a rating on the site and categorizes it by topic, quality and maturity level. No sites are blocked unless the user has subscribed to a service that allows them to set their rating preferences

As previously mentioned, Internet filtering software uses a combination of these methods in varying degrees. Each product will be different and part of the process of examining the software will include how well the vendor is able to provide you with answers about how the software works.

Some points to think about when considering Internet filtering in your environment:

• What are the views of your community regarding filtering Internet access?
• What alternatives do you have for managing Internet access?
• Do you have an AUP in place?
• Is desktop security an issue?
• Are there firewall issues that may impact updates?
• What are the capabilities of your local hardware and software?
• How much time do you have to maintain the filtering system?
• How much expertise do you have to configure the filtering system?
• What kind of a budget do you have to handle this issue?
• Can you find funds from other sources to assist if needed?

When looking at filtering software or services:

• How tamperproof is it?
• What methods of filtering does it employ?
• How much can you modify or provide input into those methods?
• How much modifying will have to be done by you?
• What type of support does the vendor include?
• How are the updates done and how often?
• Does it have an authorized override feature?
• Are other services included that your environment would find beneficial?
• Can they provide you with a demo at no cost?
• Is there a similar product or service to compare it with?

These are only a few of the questions that you should answer before making any decisions about filtering Internet access in your environment. No matter what decision you make, you will be faced with detractors. The best thing you can do is make yourself aware and be ready to answer for your decision. There is plenty of information available on the Internet both for and against Internet filtering that you can tap into to help you make your decision and formulate your response to the inevitable challenges that will arise. For further information, I recommend you consult the Internet rather than any books published on the topic as the technology is changing much too fast for information in book form to retain validity. I have included here a list of URLs that reference Internet filtering software sites and informational sites about the filtering issue in general.

That’s it in a nutshell. I realize that this is a compressed version, but it is one that I believe gives you the necessary basics. We discussed the types of filtering currently in use, we examined the methods they employ to filter Internet content, and went through a list of questions designed to assist you when considering Internet filtering in your environment. I’m confident that with a bit of research and planning, you can go back to your schools and libraries and make well-informed decisions on Internet filtering.

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