Great Circle Associates Firewalls
(October 1994)
 

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Subject: Re: very simple packet filters
From: lavondes @ tidtest . total . fr (Michel Lavondes)
Date: Tue, 18 Oct 1994 16:28:27 +0000 (GMT)
To: PETER @ cardiology . medrmh . unimelb . edu . au (Peter Summers Computer Engineer Cardiology)
In-reply-to: <14E842C45B9 @ cardiology . medrmh . unimelb . edu . au>; from "Peter Summers, Computer Engineer, Cardiology" at Oct 18, 94 8:21 am
Reply-to: lavondes @ tidtest . total . fr
Resent-date: Wed, 19 Oct 1994 08:19:53 +1000
Resent-from: "Peter Summers, Computer Engineer, Cardiology" <PETER @ cardiology . medrmh . unimelb . edu . au>
Resent-message-id: <01HIGCNWQNAQ002IQ7 @ muwayb . ucs . unimelb . edu . au>
Resent-to: firewalls @ greatcircle . com

Peter Summers, Computer Engineer, Cardiology wrote :
> 
> > Do your PCs need to talk to your Unix box ? Do they need to talk to the
> > outside ? If the answer to both is yes, there is a risk (btw, what do you
> > mean by "significant" ?)
> 
> The PCs need to talk to the UNIX box.
> 
> The users of the PCs would like to access the Internet, for all the
> usual reasons (news, mail, Mosaic, etc.).
> 
> By significant, I mean a risk that would preclude giving the PC users
> Internet access.
> 
> > Obvious backdoors are Telnet (first from to the outside to a PC, then from
> > that PC to the Unix box) and FTP (send a file to a PC, then from there to
> > the Unix box using 3rd-party FTP and/or Telnet). Depending on your set-up,
> > there may be others.
> 
> The system is installed in a pathology lab.  Clearly, anything
> capable of allowing incoming Telnet would need to be banned.  My
> question is really, what other PC software might be security risk?
> Could FTP, outgoing Telnet software, or Mosaic be a problem?
> 
Well, *anything* can be a problem if it has the right security holes active :-)
More to the point, I don't *think* outgoing telnet or FTP is a likely risk.
Incoming FTP (ie FTP server on your PCs) could be, though. You also need to be
careful about such things as mail/news, but they should be OK if properly done.
Avoid unauthenticated servers such as BOOTP/TFTP. As to Mosaic, I still don't
understand enough about how it works for a meaningful answer. Anybody out there
cares to field that one ?

BTW, I'm on firewalls, so you don't need to send to me *and* firewalls. Feel
free, however, to forward this to firewalls (I didn't send it there, since
I'm not sure you're a member).

Regards
-- 
Michel Lavondes
E-Mail : lavondes @
 tidtest .
 total .
 fr
         lavondes%tidtest .
 total .
 fr @
 pegase .
 total .
 fr (if previous addr rejected)
Tel : +33-1-4135-4198
Fax : +33-1-4135-4189


References:
Indexed By Date Previous: Re: Better version of tftp?
From: Adam Glass <glass @ NetBSD . ORG>
Next: Re: Sidewinder and Virus Scans
From: smb @ research . att . com
Indexed By Thread Previous: Re: very simple packet filters
From: "Peter Summers, Computer Engineer, Cardiology" <PETER @ cardiology . medrmh . unimelb . edu . au>
Next: Burgler Alarums
From: padgett @ tccslr . dnet . mmc . com (A. Padgett Peterson, P.E. Information Security)

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