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April 2010The monthly newsletter by Felgall Pty Ltd

My Word

Internet Filtering

The Australian Government are in the process of arranging to implement filtering on the internet to remove the ability of people in Australia to access certain illegal material on the internet eg. child pornography. While their ob jective in implementing this filter is to be admired, there are problems with what they are doig. The overall concept of what they are trying to do is so good that I suggest that in terms of the concept that they haven't gone far enough. They shouldn't just filter access to that material, they should implement a world wide filter to prevent such material being able to be uploaded to the internet in the first place and they should use their time machine to go back and implement the filter from when the internet was created so that such material can never have been uploaded.

Now obviously at some point in reading the above paragraph you will have reached the conclusion that what I am suggesting is impossible to implement. The only thing that might differ between different readers is at what point in reading the suggestions in the above paragraph that you decided that the suggestion being made is impossible to implement. That's because the different suggestions in the first paragraph differ in how obvious that it is that it is impossible to implement that particular idea. In fact each and every suggestion in the first paragraph is equally impossible to implement with only how obvious that impossibility is differing between them. What the Australian government propose to implement has as much chance of actually working as their time machine does - none whatsoever.

No technical solution to filtering the internet is ever going to work unless someone does use a time machine to go back in time to change the way the internet was designed in the first place. That no form of filtering is ever going to work is obvious from the way in which the home filters that you can already download and install and run on your own computers do not work effectively unless you use the type of filter that works off a whitelist. With this sort of filtering, everything is blocked unless it has been added to the whitelist. Even there things can slip through if someone with access to update the content of one of the whitelisted sites uploads something inappropriate. Of course the site will then eventually be removed from the whitelist and so will no longer be accessible.

The problem with whitelisting though is that there are millions of new sites being added to the internet each day and the whiltelist needs to be manually updated to add those sites that are allowed to be accessed. China uses filtering of this type where people inside China can only access sites from outside of China that have been approved by their government. This is not the sort of filtering that the Australian government are proposing. In the real world this sort of filtering is only suitable for use with young children where you want to limit their internet access to a small number of sites that you have already checked out yourself in advance.

There are three other types of internet filter you can install on your local computer. One of these doesn't actually block access to anything but does log every site visited. This makes it suitable for older children where you let them know that the log is being kept and so even though you are not looking over their shoulder while they are using the internet you will still be able to tell where they went just as if you were looking over their shoulder. This 'big brother is watching' approach may work if you install it on your own computer to discourage your young teenagers from visiting inappropriate sites. This form of filtering must be installed onto the specific computer though. Once you look at implementing such a logging system on the internet itself you run into the problem that the only identifying information available is the IP address and that only identifies the ISP and does not identify which particular customer of that ISP was using that IP address at that time. You's also need to force the ISPs to keep records of who was using which IP address when in order to be able to identify which account accessed the inappropriate site. You still wouldn't necessarily be able to identify who it was that was using the computer at the time. Anyway no government has attempted to implement this type of filtering.

Another type of filtering you can run on your own computer uses a heuristic approach of typing to indentify inappropriate sites based on their content. A web page will be blocked due to its containing certain words. A picture will be blocked based on it containing a certain percentage of the picture content being particular colours. This sort of filtering will block a percentage of the sort of sites you want blocked but will also block some sites that are perfectly legitimate and which are not supposed to be blocked. Depending on how strictly you set the filter you can block more of the inappropriate sites at the cost of also blocking more innocent sites or you can block fewer inappropriate sites in order to block fewer innocent sites. In order to not block any innocent sites you need to turn the filter off. If you want to make sure you block all inappropriate sites then you are going to block a significant fraction of the innocent sites as well. This form of filtering really surves no useful purpose since it cannot block all inappropriate sites and will block innocent sites.

The fourth and final type of filter is the least effective of all and is the type of filtering that the Australian government is looking to implement. This type of filter uses a blacklist to specify those sites that are to be blocked. All sites not on the blacklist are accessible but access is slightly slowed while a lookup of the blacklist is done in order to confirm that the site isn't on the blacklist. If you implement this type of filtering at home then you need for someone to provide you with a list of inappropriate sites for your blacklist as otherwise you'd need to visit all those inappropriate sites yourself in order to determine that they are inappropriate and to add them to the list. This means that you are relying on the provider of the list to have not mistakenly placed an innocent site on the blacklist. Also since those on the blacklist will not want their sites blocked, once they find out they are blacklisted they will arrange a new address for their site that isn't blocked and so their site will then still be accessible despite their original address being blacklisted. Their is no limit to the number of addresses they can switch to for their content and so the blacklist will just continue to grow and grow with millions of entries being required in order to not succeed in blocking even one site.

This blacklist approach is the one the Australian government has decided to take. This approach will slow down the internet access of everyone in Australia while the site they are trying to access is looked up on the blacklist. As blacklised sites set up on more and more addresses to bypass the blacklist the list will grow longer and the time taken to check addresses will grow making internet access progressively slower with the blacklisted sites still accessible via some new address not added to the blacklist yet. That means that the introduction of the filter will slow down everyone's internet access without it achieving its intended purpose at all.

What is worse with the blacklist system is that innocent sites can be incorrectly added to the blacklist and since they have no reason to expect to be blacklisted they will not be setting up on new addresses to get around the block. The blacklist will therefore be effective at blocking access to these innocent sites incorrectly blacklisted even though it is ineffective at blocking access to the sites that are supposed to be on the blacklist.

The other problem with filtering isn't a technical one but rather relates to different viewpoints. While most may agree on extreme types of inappropriate material such as child pornography being blocked, just where do you draw the line. Different people are going to have different ideas on just what represents inappropriate material and so the extent to which the filtering is to be applied in the future is going to depend on just who it is that has control of the filtering. An atheist may decide that any mention of religion is inappropriate and add all religious sites to the blacklist. A religious fundamentalist may decide that all references to science are inappropriate and add science sites to the blacklist. If we were to add all the sites that anyone considers inappropriate then we may as well turn the internet off as everything would be blacklisted. Such decisions on what is and isn't inappropriate in defining a blacklist for home use is workable in that different blacklists can be implemented based on the beliefs of those in control of the home computers. A government run filter though runs into difficulties in that no matter whee they draw the line on what is to be filtered there will be groups pushing to have additional types of material added to the blacklist. Those groups may be able to apply a lot of pressure and get their particular viewpoint implemented on the filter in the future. The only way to prevent such future pressures will be to not implement such a filter on the internet in the first place and to leave it to the individuals themselves to implement the filters on their own computers.

Note that any form of filter doesn't prevent those implementing the filter from visiting any particular site. Any site their filter blocks will be one that they have no intention of visiting anyway. The purpose of a filter is to block where other people can go. While this is appropriate for small childred and even for teenagers, it is reasonable to expect that adults ought to be capable of deciding for themselves which sites they should and shouldn't visit based on the law and their own beliefs.
 

On Site

As the tenth anniversary of when I started working on this site approaches, it sometimes gets hard to decide what to write about that is computer related that I haven't already covered. In recent years the internet related part of the site has got the bulk of the new pages but when I first started the intention was to try to cover many different aspects of computer software in a more even way. If anyone has any suggestions for information that they'd like to see added that isn't related to the internet but which is still appropriate for one of the secions of the site then please go ahead and suggest it.
 

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