[CentOS] Detecting empty office doc containing virus macro

[Gary Stainburn]

On Wednesday 28 October 2015 21:12:19 Ned Slider wrote:
> On 28/10/15 11:55, Gary Stainburn wrote:
> > We are receiving LOTS of emails that contain empty XLS or DOC documents
> > with embedded virus macros.  These are getting past SPAMASSASSIN, Clamav
> > and Kaspersky.
> >
> > I'm trying to write a filter for EXIM to block these emails but I need to
> > know a good, quick, command-line to detect an empty doc with a macro.
> >
> > Is there anything available that I can use??
> >
> > I have managed to write a PERL script to detect empty xls xlsx, doc and
> > docx files but I cannot detect whether they have any macros embedded
> >
> > Gary
>
> If you've got a script to detect empty docs then it should be relatively
> easy to detect these. I assume empty attachments are not normal in your
> mail flows?
>

I have come to the conculsiion that I am just going to have to stick with 
detecting empty documents and forget the macro checks.

> I would look to write some custom SpamAssassin rules, maybe
> incorporating your script, to detect these and filter them out.

I would love to be able to write custom Spamassassin rules but do not know how 
to do this. All I have done in the past is add small pattern matching rules 
to local.cf

Another rule I would like to add to Spamassassin is to catch emails where the 
subject starts with the email local part in brackets as we get a LOT of those 
too.

>
> Are you able to post some examples to pastebin?

http://www.stainburn.com/virus_files/I0000040777.doc
http://www.stainburn.com/virus_files/FAX_20151028_1445421437_89.doc