An E-mail processor, from Baltimore Technologies. Part of their MIMEsweeper product line.
The name probably suggests what this program does. It takes image E-mail attachments and uses AI routines to determine if the image is pornographic in nature - and junks all pr0n it sees, of course. The excuse for this is to prevent sexual harassment on workplaces.
Of course, no one has yet made a good algorithm for detecting if the image is pornographic or not.
Dan's Data reviewed PORNsweeper carefully and they found out that it was pretty good at blocking pr0n, but it also detected an awful lot of false positives when seeing non-pr0n pictures.
My favorite pictures that PORNsweeper falsely blocked were the pictures of George W. Bush and praying Bill Gates... not that I'd have anything personal against either =)