Blocking *.bin Files in EOP can cause block of Office Documents

Hi All,

I just want to write a short Blog Article about Exhange Online Protection (EOP) Malware Filter regarding the *.bin Attachments.

Just be aware, that when Adding Linked or Embedded Objects in Office Documents (like PowerPoint), the Objects are added as *.bin Objects and might be catched by the Malware Filter.

If you rename the *.pptx or add *.zip at the end you can open in with Windows Explorer or any other ZIP Tool.

As you can see there is a “oleObject1.bin” File in the ppt\embeddings Folder

I have made a Test Anti-Malware Filter policy with just one Recipient addet.

The setting is to Reject a Mail with an NDR

And in the FileTypes there is *.bin

I send now a Mail to that Recipient with the PowerPoint that contains this Embeddet Object.

And i get an NDR

In the Details we can see that this was because of the Attachment and the Malware Filter.

As an Admin you can see that also in the Threat Explorer Details.

Andres Bohren