Skin, or rather its tones, is the key to tracing graphic pornography in e-mail, says pornography-scanning software marketeer Lindsay Durbin.
According to Durbin, product marketing manager for Content Technologies, supplier of e-mail porn-detection add-on Pornsweeper, the higher the percentage of skin colour in a graphic e-mail attachment, the higher the chance that the attachment contains an image of a naked person.
Pornsweeper is designed to detect graphic porn in e-mail by recognising the colour of human skin in those attachments. The product matches the colours in an image with the product's own 24-bit catalogue of possible human skin colours, Durbin said.
Pornsweeper is an add-on to Content Technologies' existing non-porn-specific e-mail content security product Mailsweeper.
The product analyses how many separate flesh-coloured "blobs" appear in an image. If an image contains only one flesh-coloured "blob" it is more likely to be pornographic, Durbin said.
If Pornsweeper finds a high proportion of an attached image is one unbroken "blob" the colour of human skin, it traces that image for human eyes. The further apart the eyes, the more likely the image is to be dominated by a human face and the less likely it is to contain nudity, Durbin said.
"If there isn't a face, or much face, there's a chance it's porn," he said. "It's all really about skin."
Because of the product's reliance on skin colour as a key to detecting nudity, attachments containing black and white pornographic images are immune to detection, Durbin said.
Content Technologies officials said Pornsweeper would cost around $2000 for a company with 100 employees using e-mail. However, that cost does not include the cost of implementing Mailsweeper, which is crucial to its running. To install both products in a company of 100 e-mail-attached employees would cost around $8000, they said.