MC285906 – Anti-malware policy : Common attachment filter : Additional file types block by default

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check before: 2021-10-02


Defender, Exchange, Microsoft Defender for Office 365


Online, Web, World tenant


In development

Change type:

Feature update, User impact, Admin impact




The 'Common attachment filter' option in the 'Anti-malware' policy helps the Administrator configure the file types (based on file extension) which need to be blocked in the emails. This block action is applied anytime the file type of any attachment in the email matches this configurated file type list.
The current pre-configured list has 96 file types. Of these 96 file types, 10 files types are selected by default in the block list. When a new policy is created, these 10 file types are selected, to be blocked, by default. Administrator can make changes to this selection by selecting more file types or making changes to existing file types. If the Administrator chooses to extend this behavior to more file types, then this is possible using PowerShell option.
As part of this enhancement to the feature, we are adding three additional file types to the default selection list. The newly added file types are '.iso', '.cab' and '.jnlp'.
[Key points]
Microsoft 365 Roadmap ID 85611
Timing: We expect this feature to begin rolling out in early October and expect the rollout to be completed by late October.
Roll-out: tenant level
Action: Review and assess.

Change Category:


General Availability



task type:
Plan For Change

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