Such a scenario seems to be a common problem. To solve this, the ASSP_AFC
plugin got some improvements. Because these changes are security related,
I'm still testing the new code.
The new code (assp.pl and APPS_AFC.pm) are available at SF-SVC in the test
folder.
What is changed?
A new exception ':HLMSOLE' (HarmLess MS-OLE files) was added. If this
exception is used and a MSOLE file is detected in an attachment, the OLE
file is extracted and every single content (file) in the OLE is scanned
for virus and (if configured) for executable code.
A MS-Office-Macro is an OLE file in every case. Using a combination like :
exe\-bin|:MSOM|:HLMSOLE|:CSC will lead in to the following behavior.
- macros are not blocked
- script code (VBA for example) is not blocked
- MS-OLE (also macros) are not blocked as long as they not contain
executable code or a virus
What are the requirements?
The perl modules OLE::Storage_Lite and Email::Outlook::Message must be
installed.
>They regularly violate SPF
Override the SPF record for this domain in assp and block strictly on SPF
faults for this domain.
Record all the sender addresses, put them in to a group and configure an
attachment blocking (at runtime) exception for this group of people.
How ever, if the company uses a large email provider (gmail, microsoft,
....) to deliver there mails - you are lost in case spammers using the
same provider. SPF will pass and usinf the right sender addess is easy.
If there is no way to get this 100% solved, create an email account for
your company (gmail, ms, ....), give the email address to the shipping
company. Collect the emails from the provider and rewrite the recipient
address in assp to hide the original recipient address..
Thomas
Von: "K Post" <nntp.p...@gmail.com>
An: "ASSP development mailing list" <assp-test@lists.sourceforge.net>
Datum: 14.06.2018 17:34
Betreff: [Assp-test] UserAttach sender & recipient matching?
I'm looking for a magical way to do do something where a UserAttach rule
could work for a pair, like
to:OurOneUser@OurCharity.org_from:*@TheShippingCo.com=>block=> (the list)
Here's the scenario:
A giant international shipping company that we work with needs to be able
to send us excel files with macros in them. They will not provide the
files any other way and they are critical to our charity. A seemingly
ever changing list of people at this external domain send these files, but
only to ONE of our people here. They regularly violate SPF, don't
consistently DKIM sign - and they're so incredibly large that there is no
hope of change on their end.
I am trying to avoid doing the exception for the whole sender domain
because it's a domain that's commonly used to send spam/scam emails too.
So, an exception like:
*@ABC.com => block =>
exe\-bin|:MSOM|:MSOLE|url|ade|adp|asx|bas|bat|dot|dotx|xlt|xlts|bin|chm|cmd|com|cpl|crt|dbx|dll|exe|hlp|hta|htb|inf|ifs|isp|js|jse|lnk|mda|mdb|mde|mdz|mht|msc|msi|msp|mst|nch|pcd|pif|prf|ps1|reg|scf|scr|sct|shb|shs|vb|vbe|vbs|vba|wms|wsc|wsh|rar|dotm
(which has the :MSOM exception and doesn't have xlsm listed like our
regular block does)
would work, but then lets the scammers send scam Excel macro files to
everyone. No good.
With my idea of having user attach be matched only for one recipient only
if it's from the shipper domain, we limit the exposure a bit.
Thoughts? Other ideas?
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