MS Doesn't completely block spam with faulty attachments

Fri Sep 2 13:58:07 IST 2011

  _____  

From: mailscanner-bounces at lists.mailscanner.info
[mailto:mailscanner-bounces at lists.mailscanner.info] On Behalf Of Joolee
Sent: Friday, September 02, 2011 6:20 AM
To: MailScanner discussion
Subject: Re: MS Doesn't completely block spam with faulty attachments

A feature that i would like to be able to disable ;)

"Why would you want to spend precious resources on a meaningless check, when
you already decided to stop the offending attachment?!"
To inform my paying user why the contract he's been waiting for was blocked.

I think I already made quite clear why it's not an option for me to
completely block them. I can't see why other users can't be bothered by it,
maybe they just accept that they can't solve it? (Not my way of handling
problems)
[Rick Cooper] 

Seems like you need to modify your multiple extension rules to include
dangerous extensions and ignore the rest. for instance a rule like
/\.(exe|com|bat|vbs)\..+$/

would allow "something.good.doc.pdf" but would catch
"something.bad.doc.exe.pdf". Of course you would want (exe|vbs|com|bat) to
include extensions that you feel should be blocked in the multiple extension
rule. I had to change mine long ago because there are a *lot* of people who
create files names like "something.good.09.01.2011.doc". The default rules
are there for out of the box functionality but you can modify them as
required for your given situation and clearly you need to pass multiple
extensions that are not likely to be malware. With MailScanner you can
generally solve any issues without accepting the default rules, or asking
for something else to be added either. There has been discussion in the past
regarding being able to define the order in which the processing events take
place but this would require a HUGE change in the core of MailScanner and
Julian does have a job that puts food on the table. Unless MailScanner
evolves into a programming team or group that is not likely to ever happen.

On 1 September 2011 23:07, Glenn Steen <glenn.steen at gmail.com> wrote:

That's not a problem, it's a feature... And a much needed one at that!
Why would you want to spend precious resources on a meaningless check, when
you already decided to stop the offending attachment?!
Don't deliver it at all, if it bothers you;-) 

Cheers
-- 
-- Glenn

Den 1 sep 2011 19:12 skrev "Joolee" <mailscanner at joolee.nl>: 

> The problem with the current spam is that they're blocked for containing
exe
> files, not double file extensions (Although they woul've hit that one if
> exe's were not clocked.)
> 
> Only quick temporary solution is to disable all file-name validation
because
> this can occur with more than just exe files and double extensions. This
is
> no final solution though.
> 
> On 1 September 2011 18:40, Kevin Miller
<Kevin_Miller at ci.juneau.ak.us>wrote:
> 
>> **
>> Easiest thing to do in that case is to comment out the line in
>> filename.rules.conf that disallows double extensions. The message will be
>> accepted as normal and go through the additional tests (is it an
executable,
>> is it a virus, is it spam, etc.)
>>
>>
>> ...Kevin
>> --
>> Kevin Miller Registered Linux User No: 307357
>> CBJ MIS Dept. Network Systems Admin., Mail Admin.
>> 155 South Seward Street ph: (907) 586-0242
>> Juneau, Alaska 99801 fax: (907 586-4500
>>
>>
>> ------------------------------
>> *From:* mailscanner-bounces at lists.mailscanner.info [mailto:
>> mailscanner-bounces at lists.mailscanner.info] *On Behalf Of *Joolee
>> *Sent:* Thursday, September 01, 2011 7:32 AM
>> *To:* MailScanner discussion
>> *Subject:* Re: MS Doesn't completely block spam with faulty attachments
>>
>> I agree that it isn't a good idea to notify the sender of a spam or virus
>> message I'm not planning to do that, I know the troubles of backscatter.
>>
>> What I've configured is that if a user sends a completely normal
>> (non-virus, non-spam) E-mail but with, for instance, a file named
>> "CurriculumVitae.doc.pdf" (default output for a lot of PDF printers). The
>> server sends out a warning to sender and the original message stripped of
>> it's attachment to the recipient of the message. Notifying the sender is
not
>> strictly necessary but if this is only done for such non-virus, non-spam
>> message, it isn't a problem either.
>>
>> The situation that bugs me is when some spam message with a file named
>> "CurriculumVitae.doc.pdf" is received. The message hits the filename rule
>> and* isn't processed any further to check if its a spam message*. Because
>> it isn't processed any further, the warning messages are send out to both
>> sender and original recipient.
>>
>> As I stated before, I can disable the sender notification. What I can't
do
>> is tell my customers (the recipients) that such wrongly named files, most
>> containing important documents, are silently discarded. Sending spam to
my
>> customers that could have been recognized isn't an option either.
>>
>> The simplest solution, I think, would be to *continue processing* the
>> message after a file name rule is hit, decide if the E-mail is HAM and in
>> that case, send out the notifications. If the E-mail is spam, silently
>> discard it.
>> It would add a bit of load to the server but stopping spam is what it's
all
>> about, isn't it? :P
>>
>> On 1 September 2011 16:34, Julian Field
<MailScanner at ecs.soton.ac.uk>wrote:
>>
>>> He's probably switched on some "Notify Senders" options. Bad idea :-(
>>>
>>>
>>> On 01/09/2011 12:32, Martin Hepworth wrote:
>>>
>>>> what version of MS?
>>>>
>>>> I never inform the sender of junk as you end up with fake messages sent
>>>> out.
>>>>
>>>> --
>>>> Martin Hepworth
>>>> Oxford, UK
>>>>
>>>>
>>>> On 1 September 2011 08:17, Joolee <mailscanner at joolee.nl <mailto:
>>>> mailscanner at joolee.nl>**> wrote:
>>>>
>>>> Hallo Everybody,
>>>>
>>>> I've experienced a small flood of virus E-mails. These E-mails
>>>> (subj.: "ACH Payment *random number* Canceled") contain
>>>> attachments named like: "report_082011-65.pdf.exe"
>>>> They obviously get blocked by the "no executables" and "No double
>>>> file extensions" rules. The problem is that after blocking them,
>>>> an automated E-mail is send to the original recipient and the
>>>> (faked) sender of the message, informing them of the blocked
>>>> attachment.
>>>>
>>>> Had the E-mails been processed further, they would've probably hit
>>>> the virusscanner (not tested) or spamassassin (gives a score of 27
>>>> when tested) and the E-mail would've silently been discarded as a
>>>> virus / spam / phishing.
>>>>
>>>> Is it possible to let the MailScanner continue it's processing
>>>> when hitting the file name rules and / or running the filename
>>>> rule at a later time?
>>>> --
>>>> MailScanner mailing list

>>>>
mailscanner at lists.mailscanner.**info<mailscanner at lists.mailscanner.info>
>>>>
<mailto:mailscanner at lists.**mailscanner.info<mailscanner at lists.mailscanner.i
nfo>>
>>>>
>>>>
>>>>
http://lists.mailscanner.info/**mailman/listinfo/mailscanner<http://lists.ma
ilscanner.info/mailman/listinfo/mailscanner>
>>>>
>>>> Before posting, read
http://wiki.mailscanner.info/**posting<http://wiki.mailscanner.info/posting>

>>>>
>>>> Support MailScanner development - buy the book off the website!
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> Jules
>>>>
>>>> --
>>>> Julian Field MEng CITP CEng
>>>> www.MailScanner.info
>>>>
>>>> Buy the MailScanner book at www.MailScanner.info/store
>>>> Need help customising MailScanner? Contact me!
>>>>
>>>> PGP footprint: EE81 D763 3DB0 0BFD E1DC 7222 11F6 5947 1415 B654
>>>> Follow me at twitter.com/JulesFM
>>>>
>>>> 'It's okay to live without all the answers' - Charlie Eppes, 2011
>>>> 'All programs have a desire to be useful' - Tron, 1982
>>>>
>>>
>>> --
>>> This message has been scanned for viruses and
>>> dangerous content by MailScanner, and is
>>> believed to be clean.
>>>
>>> --
>>> MailScanner mailing list

>>> mailscanner at lists.mailscanner.**info
<mailscanner at lists.mailscanner.info>
>>>
http://lists.mailscanner.info/**mailman/listinfo/mailscanner<http://lists.ma
ilscanner.info/mailman/listinfo/mailscanner>
>>>
>>> Before posting, read
http://wiki.mailscanner.info/**posting<http://wiki.mailscanner.info/posting>

>>>
>>> Support MailScanner development - buy the book off the website!
>>>
>>
>>
>> --
>> MailScanner mailing list
>> mailscanner at lists.mailscanner.info
>> http://lists.mailscanner.info/mailman/listinfo/mailscanner
>>
>> Before posting, read http://wiki.mailscanner.info/posting
>>
>> Support MailScanner development - buy the book off the website!
>>
>>

--
MailScanner mailing list
mailscanner at lists.mailscanner.info
http://lists.mailscanner.info/mailman/listinfo/mailscanner

Before posting, read http://wiki.mailscanner.info/posting

Support MailScanner development - buy the book off the website!

-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.mailscanner.info/pipermail/mailscanner/attachments/20110902/bbdfb885/attachment-0001.html