Blocking macro-enabled Office files (docm, xlsm, etc)

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L1 Bithead

Blocking macro-enabled Office files (docm, xlsm, etc)

The available file types that can be filtered doesn't include Office documents with macros (docm, xlsm, etc).  These are being used now to sneak garbage into the network.  Is there a way to ID them or are they on the horizon for inclusion in the file blocking filters?  An innovative way that is being used is to create an xlsm file with a malicious macro in it and then replace the xlsm extension with csv.  User thinks it's just rows of text and clicks on it, Windows feeds it to Excel, and Excel opens it and runs the macro.

 

Gene

 


Accepted Solutions
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Cyber Elite

You can also block id 39154 which is Microsoft Office File with Macros. Please note that this isn't a perfect signature by far, but it does manage to take care of a good percentage of files before they hit our Barracudas 

View solution in original post


All Replies
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L7 Applicator

Hi Gene

 

The firewall will not be able to differentiate doc files with or without macros as they are basically the same file type, it will be able to identify doc files 'disguised' as CSV as it looks deeper into the file than merely the extention . You could block doc files altogether, which may be a bit over the top.

 

you could dable with custom vulnerability signatures to block .docm files or any identifyable string of data inside the fileor you could push an ActiveDir group policy preventing your users from opening these files

 

 

Tom Piens - PANgurus.com
New to PAN-OS or getting ready to take the PCNSE? check out amazon.com/dp/1789956374
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L7 Applicator

Block macros with GPO.

https://blogs.technet.microsoft.com/mmpc/2016/03/22/new-feature-in-office-2016-can-block-macros-and-...

Enterprise Architect @ Cloud Carib www.cloudcarib.com
ACE, PCNSE, PCNSI
Highlighted
Cyber Elite

You can also block id 39154 which is Microsoft Office File with Macros. Please note that this isn't a perfect signature by far, but it does manage to take care of a good percentage of files before they hit our Barracudas 

View solution in original post

Highlighted
L3 Networker

Or Subscribe to Wildfire, it does a pretty bang up job with handling them!

 

Good luck!

 

-sO

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