Home page logo
/

fulldisclosure logo Full Disclosure mailing list archives

Re: Re: E-Mail viruses
From: "Eddie " <EddieS () softhome net>
Date: Sat, 06 Mar 2004 13:06:11 -0800

Curt's suggestion works.  With only 35 email accounts at work, I farm out our email to our web host (FutureQuest) so I 
don't have to mess with running a server. 
I have had the executable attachments filter turned on from day one (day one == 3 years ago).  You send an exe 
attachment to someone in the office, it gets 
bounced back with a message to please zip the file and send again. Nobody can receive anything that will run when 
clicked.   Just this works very well and it has 
cut the viruses down to almost null.  

With MyDoom and others on the rampage, I added zip to the list, and changed it from a bounce to a black hole.  I put 
out a memo about the rename the extension 
trick.  Not a single complaint and quite a few thank you. We have not gotten one virus since I did this.   I don't plan 
to do this forever, just until MyDoom and others 
goes down a bit more, and then it's back to the bounce.  

And yes, we have Norton on each client. :) 

Eddie


On Sat, 6 Mar 2004 10:23:30 -0600, Curt Purdy wrote:

docco wrote:
What Curt Purdy is saying looks to me like a
great_pain_in_the_ass_solution.
In case the "supersecret" extension would get leaked or
compromised, which I
beleive would be absolutely not hard to achieve (by means of social
engineering, sniffing or just brute force - combinations of
three letters,
<snip>

Jeese, it's amazing how a thread can get so twisted overnight.  My original
point was that is was never necessary to hide the proprietary extension and
it would never need to change.  The purpose of blocking everything but this
extension, in our case .dps (see, I'm not scared) is to squash 99.999%
(experience has been 100% so far) of all possible infected attachments
before it ever gets to our email AV server.  Of course that percentage may
now drop if some "security expert" on this list decides to rename netsky and
send it to us.  However that would be a waist of time unless it was a 0-day,
and I doubt anyone would want to waist that on us.

In addition, it is much easier to train users to change the extension than
to "not open attachments" because they are self-motivated to do the former
if they ever want another attachment.  If you try to educate users to do the
latter, you are just setting yourself up to continually battle the social
engineering used by virus coders.

While I'm on the subject, just this morning on a nationally syndicated show,
I heard a piece on the current "virus war" and was amazed when I heard it
end with "a security expert" say "only open attachments from someone you
know".  We disabled notifications on our AV server months ago.

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

_______________________________________________
Full-Disclosure - We believe in it.
Charter: http://lists.netsys.com/full-disclosure-charter.html



_______________________________________________
Full-Disclosure - We believe in it.
Charter: http://lists.netsys.com/full-disclosure-charter.html


  By Date           By Thread  

Current thread:
[ Nmap | Sec Tools | Mailing Lists | Site News | About/Contact | Advertising | Privacy ]