DIA to list child porn sites for voluntary blocking

November 12th, 2007 at 5:30 pm by David Farrar

The DIA has announced it will make available to ISPs a list of websites hosting child porn, allowing ISPs to black access to them.

A similar scheme operates in the UK (and other countries).  I was actually involved in helping set up a test of the UK filter by DIA, the Censorship Classification office and InternetNZ.

There were two major issues looked at.  The first is whether the UK filter blocked legitimate sites which did not have material deemed objectionable and illegal under NZ law.  In other words what was the false positive rate?

The second issue was what proportion of child porn sites were blocked?

With regard to the false positive rate, the good news is that it was basically zero.  Almost every site blocked was hosting material illegal under NZ law, and if I recall from the report this wasn’t borderline stuff (a child in a bath) but clearly hardcore illegal material.

In terms of how effective it was at blacking sources of child porn, it wasn’t terribly effective as the number and nature of sites changes daily, so the filter isn’t a universal solution that blocks everything illegal. But it does block some sites, without overextending itself to block legal sites. So that’s not a bad thing.

Since then DIA have also looked at other filtering solutions, and look to run their own filter list, based on info from overseas agencies, plus local reports.

This is really the only way to run a filter – to have it based on actual reports of illegal material, rather than have it “guess” if a site is objectionable based on text searches. One always gets too high a false positive rate using the latter approach. The list of banned sites will be basically updated daily, which is the only way to do it.

So all up, this looks to be a good step forward.  It is voluntary for ISPs, and won’t block all child porn sites, but it will be a useful tool in removing the profit from incredibly sick enterprises.

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