Mea culpa. A stupid little bug crept into linux-ftpd for Debian, and
some other Linux distros. Some may have fixed it, but Debian hasn't.
The effect is that ftpd now runs /bin/ls (for DIR and similar commands)
with GID=0. Does not seem terribly dangerous as I do not seem able to
trick ls into running anything, nor are there any interesting objects
thusly accessible. Would become a "root hole" if someone finds a way
to execute anything from /bin/ls (as started from ftpd).

Please see

  http://bugs.debian.org/384454

for details.

Cheers,

Paul Szabo   psz@maths.usyd.edu.au   http://www.maths.usyd.edu.au/u/psz/
School of Mathematics and Statistics   University of Sydney    Australia