Apr 05 2023 09:40 AM
Apr 05 2023 09:40 AM
We're trying to verify if we can block file uploads through the browser to all sites, unless these sites are part of an approved list or the user has an exception. We currently have a similar solution through a different vendor, but wanted to see if Defender for Endpoint is an alternative.
So, if someone creates a new site, this site would not be allowed to be uploaded to unless the domain is added to an approved list. The alternative would be to block if the file has a specific label.
Jun 05 2023 03:30 AM
Since you're wanting to set a "safe list" which will block uploads to anything not on this list, you'll likely want to leverage the service domains feature under Endpoint DLP settings in the Microsoft Purview portal.
You can set the service domains to be an "Allow" list to achieve this and will need an Endpoint DLP policy configure once you've set the list. The policy itself can have your specific user exclusions set (Endpoint DLP is still identity based).
While DLP is typically based on sensitive information, you can set the policy to block uploads based on file types and/or file extensions. As you mentioned, you can also scope it to block based on a specific sensitivity label applied to the file.
Jun 06 2023 09:32 AM
@miller34mike, I tried creating a custom DLP policy under https://compliance.microsoft.com. Scoped it to devices and MCAS, yet I can't see any action that allows me to block the upload to the web page. What am I doing wrong?
Jun 06 2023 09:43 AM
This is due to selecting both Devices and MDCA. When you scope to multiple locations, you only get the options that are available in both locations.
To set and Endpoint policy to block service domain uploads you will need to set the policy to Devices only and then within the rule, you will see service domain uploads.
To see this option, select actions > Audit or restrict activities on devices and it will be the first checkbox that you can select.
MDCA from a DLP perspective would not help you in this scenario.
To set your allowed list of service domains, which means everything else gets blocked, go to compliance.microsoft.com > Data loss prevention > Endpoint DLP settings and find the drop-down for Browser and domain restrictions to sensitive data. Make sure the drop-down for block/allow is set to allow and then set your appropriate sites.
Jun 06 2023 10:49 AM
Jun 07 2023 05:04 AM
Jun 07 2023 10:16 AM
@WilliamLeininger , thanks for this. I wouldn't want to classify/label documents. The endpoint should catch that the user is uploading files to a blocked website and prevent the action.
Jun 07 2023 10:19 AM
Just to confirm, are you performing your testing on a Microsoft Purview Onboarded device and using an Azure AD Identity with an E5 license to log in to the machine?
Jun 07 2023 10:38 AM
@miller34mike, yes. Full E5 licensed tenant, device enrolled in Intune and onboarded in MDE as per the device inventory (screenshot below).
Jun 07 2023 10:44 AM
Perfect! The final check to perform is under settings within the compliance portal at the link below, confirm that device onboarding has been enabled and that the same device from MDE shows up under Purview (it may take up-to an hour to complete the onboarding). Enabling Device onboarding within the compliance portal will automatically ingest all MDE-onboarded devices into purview, which is the final step to make sure that Endpoint DLP policies can be pushed to the device.
Jun 07 2023 10:49 AM
Jun 07 2023 11:01 AM
do you see the cloud upload activities within Activity Explorer?
also, I do usually recommend including the “.” In the extension, like .docx
on the onboarded devices page, you should be able to select a device and see what policies are active on it. Can you confirm this policy appears for the test device?
Jun 07 2023 11:37 AM - edited Jun 07 2023 12:19 PM
@miller34mike , nope, the upload isn't even visible in the Activity Explorer. In terms of the extensions, I entered them with the "." yet it got removed.
Interesting thing though... if I go on the onboarded devices page and look at the overview of the machine, the MDE Enrolment status is N/A. This gives me something to dig into....
Jun 07 2023 01:25 PM
I'm going to duplicate your policy and blocked domains to see what my test results in.
The MDE status is because you're managing it with Intune versus using Microsoft Defender for Endpoint Security Configuration Management.