Re: Securing email by inhibiting urls

[Marcus Ranum <mjr () ranum com>]

 Chris wrote:
> Until I can disable a users ability to click a url in an email that appears
> to come from a trusted source, I'm fighting constant infection.  We
> regularly spot infections (read WE, not our security systems), that are
> resident in our network and have been there days/weeks/months.  We currently
> have at least one that we are watching to see what it is trying to do before
> shutting it down....

Stupid users, too much connectivity, good security - you can have
any two.

I'm guessing that when you say "trusted source" what you mean
is "apparently trustworthy source" - not that you actually have a
list somewhere of trusted sources. If you had a list of trusted
sources then you could put in a firewall that did URL filtering
then have 2 group policies: "users who click on bad URLs"
and "users who are careful what they click on" Only allow
"users who click on bad URLs" to go to the trusted destinations
and deny everything else.

But it sounds like you've got an impossible problem: you're
being asked to solve end-user trust with technology and still
maintain a fairly open network. That's not going to happen,
though surely you can thrash painfully about playing network
whac-a-mole.

mjr.

--
Marcus J. Ranum         CSO, Tenable Network Security, Inc.
                        http://www.tenable.com

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