Great Circle Associates Firewalls
(September 1995)
 

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Subject: Re:
From: "Grant M. Fengstad" <G . Fengstad @ CdnAir . CA>
Date: Thu, 28 Sep 1995 10:31:36 -0700 (PDT)
To: Brent Chapman <Brent @ GreatCircle . COM>
Cc: DEEVEE @ HOUVMSCC . lsis . loral . com, firewalls @ greatcircle . com
In-reply-to: <v02130545ac90a3d9864c @ [198 . 102 . 244 . 40]>

On Thu, 28 Sep 1995, Brent Chapman wrote:

> At 7:32 AM 9/28/95, DEEVEE @
 HOUVMSCC .
 lsis .
 loral .
 com wrote:
> >Subject:Mail Proxy
> >
> >
> >
> > Does anyone have a mail proxy that will check incoming/outgoing mail for
> > attachments(executable code) and discard them? We would like to install a
> > mail proxy on one of our firewalls that would do this so we could ensure
> > that (executable) attachments would not enter our 'secure subnet'. I know
> > we shouldn't allow mail in at all but it is a customer requirement. Any
> > help would be appreciated. (By the way, we're interested in a mail proxy
> > that's been tested). Thanks, Dee Veasey, Loral Space Information Systems.
> 
> How do you recognize executable code?  What if it's been compressed, or
> encrypted, or uuencoded or something?  You could block any message with
> attachments, but what if it's sent as part of the body, rather than as an
> attachment?  And what exactly do you count as "executable code"?  Is a
> Microsoft Word document "executable code", because it might contain
> WordBasic subroutines or programs?
> 
> I don't mean to make light of your situation, but you've just opened
> Pandora's box.  Your fairly simple question definitely does NOT have a
> simple answer.
> 

Sure it does.... Simply don't take in ANY mail :)

Bottom line appears to be that one must count on having some form of risk 
when connecting to the Internet.  What that risk is can obviously be 
minimized by sound judgement and good firewall policies..



References:
  • Re:
    From: Brent @ GreatCircle . COM (Brent Chapman)
Indexed By Date Previous: Re: CERT and Firewalls BOFs
From: mokbelsa @ jasper . mcclellan . af . mil
Next: Re: Reading Word Documents
From: Adam Shostack <adam @ bwh . harvard . edu>
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From: Brent @ GreatCircle . COM (Brent Chapman)
Next: GSSAPI compliant aps
From: "Rev. Ben" <samman-ben @ CS . YALE . EDU>

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