(Decatur, IL)  --  A Mason County man is behind bars and charged with six counts of aggravated possession of child pornography.  Fred Tribbett, from Kilbourne, was arrested at his home on West Birch Street yesterday as part of Operation Glass House.  That's Attorney General Lisa Madigan's undercover sting which cracks down on those who download and trade child pornography online.  Investigators have tracked about 32-hundred IP addresses trading child porn in the past four months.  Thirty four people have been arrested for the crimes.  Tribbett, who is already a convicted sex offender, faces up to 90 years in prison.