US Customs Agent Don Daufenbach goes undercover by simply sitting at his computer to enter the community of Internet child pornographers.  At least 90 percent of Daufenbach's time is spent on Internet-related cases he tracks from his downtown Salt Lake Office.  His cases include the first foreign national charged by the American government for commercially distributing child pornography on the Internet.  A 34-year-old London businessman was sentenced to 23 months in federal prison last year for operating pay-per-view child pornography sites on the Internet.  Daufenbach paid to join Raymond McArthur-Jones' commercial site in 1996 after Scotland Yard tipped him to the site.  According to the Associated Press, Daufenbach was told of the site by both a convicted child pornographer in Ohio and a man being investigated for child pornography in North Carolina.  Michael Aaron Wilson, of Aurora, Colorado, received what was then the maximum sentence of three years in prison last April.  Wilson was accused of being the channel operator for the Boy Torture Channel on the Internet.  Images were shown of underage males being sexually abused and tortured.