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RE: [inbox] Re: E-Mail viruses
From: "Curt Purdy" <purdy () tecman com>
Date: Fri, 5 Mar 2004 17:27:16 -0600

Incident List Account wrote:
Curt, be carefull not to strain your arm patting yourself on
the back :) I actually really like your solution UNTIL the
"completely eliminates the need for antivirus on the mail
server" comment. If an outside party follows the procedure
and remnames his file to file1.inc and sends it to your user,
are you 100% confident in that outside party's attachement is
not inadvetantly infected with a virus? I agree that only
allowing a certain obscure extension through to your user
eliminates the VAST majority of the problems. I would not
however trust any file from a third party with out some sort of scan.

As a firm believer in "layered security" espoused by Bruce Schneir in which
five 80% effective layers achieve 99.8% effectiveness overall, I would never
suggest not having a mail AV server, as well as desktop AV.  The way I
developed this system was I began dropping .scr, .pif, .com, .cmd as easy
non-legitimate emails.  I then went to .exe when I got tired of the
occasional virus slipping through and told users they had to have senders
zip it prior to sending.  Now since Mydoom, I took the next logical step of
dropping everything.  Users find it just as easy to tell senders to rename
the file as to zip it.

Curt Purdy CISSP, GSEC, MCSE+I, CNE, CCDA
Information Security Engineer
DP Solutions

----------------------------------------

If you spend more on coffee than on IT security, you will be hacked.
What's more, you deserve to be hacked.
-- White House cybersecurity adviser Richard Clarke

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