[svlug] eWeek article on MS Outlook

kmself@ix.netcom.com kmself at ix.netcom.com
Tue May 16 02:39:28 PDT 2000

On Mon, May 15, 2000 at 06:21:34PM -0700, Deirdre Saoirse wrote:
> On Mon, 15 May 2000, Rick Moen wrote:
> > Interesting question to contemplate:  Do the BSD-based MacOS X Server
> > and (beta) MacOS X versions perpetuate this conceptual model?  If so,
> > then they may pose the same risk for user-authority viruses / trojans
> > / worms as we've seen lately on MS Windows 9x and NT.
> Well, for a script to execute (vs. just open), it would have to have its
> execute bit set. So, when they don't, they don't execute. Period. IOW, the
> Unix-based MacOSes respect the permissions models. AIRC, the Email client
> provided with MOSXS (which sucked) did not set attachments +x.
> The Mac does not have the same kind of tradition of scripting, so it has
> been significantly less of a problem on even MacOS.

I'm leaning toward JC Lawrence's arguments on this one, with a bit of
Rick's "open/launch" thrown in to the mix.

The issue of executable content/execute bit is irrelevant when a file
can be sourced by an interpreter.  Examples include sourcing files from
the shell running a file against an interpreter, interpreters which take
files as arguments, and files which are executed or interpreted by
mediating software.  Examples, you ask?

  - Sourcing:  
      . ./script    # syntax under Bourne & derived, 
      source file   # under csh and derived

  - Interpreting:  
      sed -f or awk -f syntax.

  - Executing:  SAS works this way -- a "SAS program" is merely a text
    file run as the prime argument of the SAS interpreter:

      sas myprog.sas

  - Execute/interpret -- most web browsers do this with various sorts of
    content.  Before you dismiss opening a .ps file in Mozilla/Linux as 
    nowhere near the same league as a .vbs file in MS Outlook/MS
    Windows, realize that PostScript is itself a fairly powerful
    programming language.  Likewise mime types *could* (though rarely
    are)  set to launch scripts on download.  More frequently, Java and
    Java script content are components of many web pages.

I concur with Rick that the idea of "opening" a file having execute
ramifications is troubling, particularly when file formats are such that
simple viewers aren't capable of determining potential for abuse, and
more powerful binary viewers aren't generally available..  However,
there's no reason an interpreter couldn't be written for Linux along
the lines of MS Word or Excel, which could open, read, and execute
content marked non-executable.  It is the interpreter which is running,
the script file need not be executable.

While the Mac may not have had the same tradition of scripting, my
understanding is that modern tools, including Unix shells, Perl, and
Python, might soon be available for the platform.  This spanks of an
argument closely paralleling "security by obscurity" with similarly
dangerous" implications.

Linux and Unix have tended to be free of the types of viruses and worms
which plague  Microsoft  platforms.  While user, file, and process
security models under Linux provide some protection from the more
grossly damaging effects of typical MS Windows viruses, a world in which
content is treated as trusted and can be easily or automatically
executed is one in which viruses and worms can be spread.  There is no
magic shield preventing the same brain-dead application architectures
which have come into being in the Windows world from emerging on the
Linux landscape.  Vigilance against this is required.


Karsten M. Self <kmself at ix.netcom.com>         http:/www.netcom.com/~kmself
    What part of Gestalt" don't you understand
GPG fingerprint: F932 8B25 5FDD 2528 D595  DC61 3847 889F 55F2 B9B0
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