This is one of my plugins for ArtEffect2/3+.

SmartMedian is a median-filter that blurs a picture without loosing sharp
edges. It can remove noise visible in large equal areas and leaving details
untouched. It is well suited to remove moirés from scanned printings without
smoothing the details out. Very useful if natural pictures are mixed with
artifical graphics/text, e.g. cover of a CD. 
Medianfilter of this type are sometimes known as despeckle filters.

There is another similar plugin available: SmartBlur

 PERMSSN    UID  GID    PACKED    SIZE  RATIO     CRC       STAMP          NAME
---------- ----------- ------- ------- ------ ---------- ------------ -------------
[generic]                11495   20032  57.4% -lh5- 2bd4 Jul 22  1999 plugins2/SmartMedian.p2m
[generic]                11493   20040  57.4% -lh5- c038 Jul 22  1999 plugins2/SmartMedian.p2n
[generic]                11495   20020  57.4% -lh5- 3dc0 Jul 21  1999 plugins2/SmartMedian.p4s
[generic]                 3478    8797  39.5% -lh5- 1bc6 Jul 22  1999 SmartMedian.guide
---------- ----------- ------- ------- ------ ---------- ------------ -------------
 Total         4 files   37961   68889  55.1%            Jul 25  1999