Path: utzoo!mnetor!spectrix!clewis
From: clewis@spectrix.UUCP (Chris Lewis)
Newsgroups: comp.misc
Subject: Re: Trojan Horse a Myth?
Message-ID: <350@spectrix.UUCP>
Date: 21 Dec 87 21:45:59 GMT
References: <459@gtx.com> <2393@killer.UUCP> <337@spectrix.UUCP> <1931@utx1.UUCP>
Reply-To: clewis@spectrix.UUCP (Chris Lewis)
Organization: Spectrix Microsystems Inc., Toronto, Ontario, Canada
Lines: 53

In article <1931@utx1.UUCP> ashley@utx1.UUCP (Ashley Oliver) writes:
>In article <337@spectrix.UUCP>, clewis@spectrix.UUCP (Chris Lewis) writes:
>> 
>> A minor quibble - have you ever used PC/MSDOS?  It's very simple to
>> break security on these machines because there ain't none.  Many BBS's
>
>Another minor quibble. It depends what you mean by 'break security'
>and I suspect Chris Lewis and I  are thinking of different aspects,

Partially.

>but I'd claim MS-DOS is a lot more secure than UNIX on the simple
>grounds that any single user/single tasking OS is inherently several
>orders of magnitude more secure than any multi user/multi tasking OS.

Um, yes, MS-DOS is infinately more secure than UNIX w.r.t. one user leaving
trojan horses around for another user.  By definition - there aren't any
other users....

On the other hand though, MS-DOS is considerably more vulnerable to
trojans and viruses from any program obtained from the "outside".
Neither the O/S or hardware is protected in any way.  Once a program is 
running, there's nothing to stop it from doing anything it wants.  
A program can read or write anything (eg: diddle the O/S) or manipulate
the hardware directly.  Leading to DOS boot blocks containing viruses
etc.  This is made more tractible by the fact that in the MS-DOS world, 
sharing of binaries between users happens much more often than in UNIX.  
In the UNIX world, most of the binary programs come from (hopefully) 
reputable software vendors.

In contrast, UNIX (as are most other Multi-user O/S's) are relatively safe 
from trojans or viruses of this type.  Because the O/S is protected by 
an MMU (except on some brain-damaged hardware like PC's), user-level 
programs cannot access devices directly, user-level programs 
cannot diddle disks directly (unless the SA goofed and made the devices 
writable), most drastic things require super-user permissions, etc.

I'm not saying that there aren't holes in UNIX - there are many
(many of which apply to ANY multi-user system).  But at least most of
them can be plugged by a diligent SA.  And almost all of the rest can be
plugged by enhancements to the kernel or shell.  Without making it "not UNIX".

It's probably impossible to make MS-DOS significantly less vulnerable to 
viruses without changing quite a bit of the spec and breaking a LOT
of existing "good" software.  Why?  Well, lots of the "good" programs
do things to your hardware that's indistinquishable from what a "bad"
program wants to do.  Eg: many "good" programs bypass DOS disk drivers
and talk directly to the controller for various reasons.  So would a virus...
-- 
Chris Lewis, Spectrix Microsystems Inc,
UUCP: {uunet!mnetor, utcsri!utzoo, lsuc}!spectrix!clewis
[Also: lsuc!clewis in a pinch]
Phone: (416)-474-1955