Re: Question about 'Hidden' Directories in ext2

[jw schultz]

On Tue, Apr 02, 2002 at 05:16:42PM -0500, Calin A. Culianu wrote:
> 
> Ok, so some hackers broke into one of our boxes and set up an ftp site.
> They monopolized over 70gb of hard drive space with warez and porn.  We
> aren't really that upset about it, since we thought it was kind of funny.
> (Of course we don't like the idea that they are using out bandwidth and
> disk space, but we can easily remedy that).
> 
> Anyway, the weird thing is they created 2 directories, both of which were
> strangely hidden.  You can cd into them but you can't ls them.  I
> 
> /usr/lib/ypx and /usr/man/ypx were the two directories that contained both
> the ftp software and the ftp root.  When you are in /usr/man and you do an
> ls, you don't see the ypx directory (same when you are in /usr/lib).  The
> ls binary we got is right off the redhat cd so it shouldn't still be
> compromised by whatever rootkit was installed.
> 
> My question is this: can the data structures in ext2fs be somehow hacked
> so a directory can't appear in a listing but can be otherwise located for
> a stat or a chdir?  I should think no.. maybe we still haven't gotten rid
> of the rootkit...
> 
> -Calin

It might be much simpler.  They may be playing with /etc/profile.
Check your shell aliases and the environment variable LS_OPTIONS.
A simple LS_OPTIONS="$LS_OPTIONS -I ypx" or
alias ls='ls --ignore=ypx' would have the effect you are
talking about.

-- 
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	J.W. Schultz            Pegasystems Technologies
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