-----Original Message-----
From:
[EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Darin Cox
Sent: Sunday, May 29, 2005
4:43 PM
To: [email protected]
Subject: Re: [Declude.Virus]
EXITSCANONVIRUS
Sounds good to me. I tend to think of both virus
and spam detection in the same breath, since I think they're stronger together
than separate... but you certainly have a valid point about moving code to
Junkmail...and it would seem more useful there as well.
I haven't seen the false positives you've seen with
the Outlook Boundary Space Gap vulnerability, but it may be due to a variation
in customer base. I'll check the logs and let you know what we've seen
over a similar timeframe.
Happy Memorial Day weekend! Don't forget to
spend some time with the fam.
----- Original Message -----
Sent: Sunday, May 29,
2005 5:35 PM
Subject: Re:
[Declude.Virus] EXITSCANONVIRUS
Darin,
My list was really only in respect to my feelings on Declude Virus and not
JunkMail. In this perspective of both however, maybe a modification where
#2 includes the potential of adding it as a test to JunkMail if it would be
beneficial, and a clarification on #3 like so:
1) Active Vulnerabilities
- Default to ON, and patch known exceptions that could be triggered by standard
E-mail clients. I would expect that such things would stay in this
category for at least a year following a patch being released for the affected
E-mail clients.
2) Inactive Vulnerabilities -
Default to OFF, don't necessarily patch issues when found (judgment
call). Add code to Declude JunkMail if useful for blocking spam.
I would expect that this category would include things that were between 1 and
3 years following a patch being issued for the affected E-mail clients.
3) Removal - Remove the code from
the Declude
Virus part of the executable. Depending on the
conditions related to the vulnerability; i.e. commonality in exploit, potential
for false positives, seriousness of flaw, etc., it would be prudent to remove
the code that detects such things after 2 or more years. Note that some
of these vulnerabilities have never been actively exploited by viruses.
Being conservative about leaving the code in for long periods I think is fine
because they would give people peace of mind and choice, but there is always
going to be a legitimate extent to which being conservative about things reach.
I think this reflects what you have said, and in
essence this is what I was indicating in the paragraph that followed.
I would definitely like to see the Outlook CR Vulnerability added to Declude
JunkMail as a scoreable test since it does hit on a good deal of spam, but I
won't use it in Declude Virus since I can only chose to block or pass and it
has daily issues with false positives for my customer base.
Other present vulnerabilities might not justify keeping the code however.
The Outlook Boundary Space Gap vulnerability trapped a total of 8 messages that
weren't otherwise detected as viruses on my system in a two week period of
time, covering over 1 million scanned messages. Of these 8 messages, all
8 were legitimate personal E-mails generated by Microsoft's own E-mail
clients. I think we could agree that if this is the long-term trend, this
code would be best removed or fixed instead of being added to JunkMail.
Alternatively, if this is still a threat with this one vulnerability (I don't
know), then the detection should be fixed. The false positives were all
the result of an error in Declude where the following header was properly
'folded', but Declude seemingly experienced an error in de-folding the headers
which led it to believe that there were spaces within the boundary. The 4
spaces at the beginning of the second line in this case is part of proper
header folding
Content-Type: multipart/alternative; boundary=
"----_=_NextPart_001_01C55D5F.F2B051DD"
This vulnerability is designed to detect spaces or
tabs within message boundaries, and apparently could be exploited to package
attachments which Outlook clients would read. The above example is not an
example of exploitable code.
RFC 2912 - http://www.faqs.org/rfcs/rfc2912.html
3.1 Whitespace and folding long headers
In some circumstances, media feature expressions can be very long.
According to "A Syntax for Describing Media Feature Sets" [1],
whitespace is allowed between lexical elements of a media feature
_expression_. Further, RFC822/MIME [4,5] allows folding of long
headers at points where whitespace appears to avoid line length
restrictions.
Therefore, it is recommended that whitespace is included as
permitted, especially in long media feature expressions, to
facilitate the folding of headers by agents that do not otherwise
understand the syntax of this field.
For this to have been the vulnerability, the
whitespace would have needed to have been within the quotes that defined the
boundary and not before it.
Matt
Darin Cox wrote:
I think most of us always consider the "greater
good" before making requests... and by their nature, most requests from
one person have benefit to many others.
I think the recommendation you outlined below is
fairly good...but again, I would not like to see potentially valuable tests
removed. Defaulting to off is good, but removing doesn't make sense when
there's value in the test. Other than an occasional Partial
vulnerability, I see no false positives with vulnerabilities from our user
base.
I do think your point about moving the code from
Virus over to Junkmail is a good one when it is no longer an
active vulnerability. I would just hate to see a valuable test
removed, and again, we see a decent amount of spam caught by Virus that doesn't
get caught by our Junkmail config.
Code can easily be broken in moving from one place to
another (Virus to Junkmail), so this may be a maintenance problem that it is
desirable to avoid. However, deprecated vulnerabilities could
potentially be more valuable there for use in weighting or combo tests to
identify particular spammers and assist with detecting their payloads.
I think this all falls under the "The more info
we have about a message, the better we can classify it"
category. Indeed, one of the main reasons we haven't migrated to
SmarterMail is the unavailability of the CMDSPACE test. We find much of
the strength in Declude is due to the variety of special tests Scott was
able to come up with.
So, with the caveat of not performing Item 3 in your
list (Removal), it sounds very good to me.
It's nowhere near #1 on my list either...just didn't
want anything useful to disappear.
----- Original Message -----
Sent: Sunday, May 29,
2005 4:22 PM
Subject: Re:
[Declude.Virus] EXITSCANONVIRUS
Darin,
I think there are many different ways to define "retire" in this
context.
Personally, I have already 'retired' the functionality on my system where I
feel that it appropriate, but when I share my opinions and recommendations, I
am often thinking of the greater good. I tend to not ask for things from
Declude that would not also be of benefit to a good number of it's users.
While having the switch alone might be good enough for the majority of us on
these lists, the majority of Declude's customers don't pay attention to the lists,
release notes, or many other things...they tend to run default configurations
with very little in the way of tweaks. These people are most in need of a
solution, though they probably mostly don't recognize the issue, and likewise
wouldn't recognize the solution. By Declude providing this functionality
and not working it into the overall approach for the best standard config and
practices, it really only serves the few of us that are paying very close
attention.
So in this perspective, the best global approach in my opinion would be to
establish a system for depricating such functionality. I would suggest
the following:
1) Active Vulnerabilities
- Default to ON, and patch known exceptions that could be triggered by standard
E-mail clients. I would expect that such things would stay in this
category for at least a year following a patch being released for the affected
E-mail clients.
2) Inactive Vulnerabilities -
Default to OFF, don't necessarily patch issues when found (judgment
call). I would expect that this category would include things that were
between 1 and 3 years following a patch being issued for the affected E-mail
clients.
3) Removal - Remove the code from
the executable. Depending on the conditions related to the vulnerability;
i.e. commonality in exploit, potential for false positives, seriousness of
flaw, etc., it would be prudent to remove the code that detects such things
after 2 or more years. Note that some of these vulnerabilities have never
been actively exploited by viruses. Being conservative about leaving the
code in for long periods I think is fine because they would give people peace
of mind and choice, but there is always going to be a legitimate extent to
which being conservative about things reach.
Regarding their use in blocking some spam, I
personally would rather Declude JunkMail tag such things, that way we could
handle this as spam, as well as the potential false positives, within the
systems that we have built to handle spam instead of the one built to handle viruses.
Active Vulnerabilities are a different story, but I wouldn't object to seeing
code added to BADHEADERS/SPAMHEADERS or another built-in test to show that
something failed a depricated check within the context of Declude
JunkMail. Some of these vulnerabilities are presently less than 90%
accurate on my system in judging between spam and ham, though the viruses
associated with them might well be deleted if they do exist and were detected
by one of my scanners (I've based this on a review of the spam folder and I
delete viruses on my system). The Outlook CR Vulnerability blocks the
most spam, but it also has the highest number of false positives by far.
Web mail generated messages from Comcast, Excite, 126.com/263.com (Chinese
equivalent of Hotmail) will all fail Outlook CR in Declude.
Does that sound reasonable? Would it provide for all of what you desire
in this respect? I do get that the folks at Declude do read this stuff
and they seem to be embracing our logic and popular opinion on the lists lately,
so I would guess that what you think does count for something. Personally
this isn't by far my #1 issue since I have already solved it with other new
functionality, but I think the process is just as if not more important as the
functionality to the product and the customer base as a whole.
Matt
--
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MailPure custom filters for Declude JunkMail Pro.
http://www.mailpure.com/software/
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