Indicators of Compromise (IoC) for Mobile devices in Defender for Endpoint

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Indicator of compromise (IoCs) is an essential feature in every endpoint protection solution. This capability gives SecOps the ability to set a list of indicators for detection and for blocking.

Back in August'21, I had published a blog on 'Creating custom Network Indicator rules in Defender for Endpoint'. As part of the MDE configuration series, I wanted to cover the creation of IoC for mobile devices as well.

Now for IoC to work, devices need to be onboarded on MDE and it is no different for mobile devices. You can head over to my posts from February'22 to check out the onboarding process for both iOS and Android mobile devices.

One thing to note here is that as of writing this blog, only IPs & URLs\domains under IoC are supported for mobile devices at this point.

When creating a new indicator (IoC), one or more of the following actions are available:
  • Allow – the IoC will be allowed to run on your devices.
  • Audit – an alert will be triggered when the IoC runs.
  • Warn – the IoC will prompt a warning that the user can bypass (Defender for Cloud Apps only)
  • Block execution - the IoC will not be allowed to run.
In this blog, I will use the Block execution action as an example. 

First and foremost, lets see how to enable Network indicators in Microsoft 365 Defender Portal. (Ignore if already done)

1. Navigate to Microsoft 365 Defender Portal > Settings > Endpoints > Advanced features > Custom network indicators.

2. Toggle the setting between On and Off and select Save preferences.

Next up is creating custom network indicator rules.

To create rules, follow the process below -

1. Navigate to Microsoft 365 Defender Portal > Settings > Endpoints > Indicators (under Rules)
2. Select the IP addresses or URLs/Domains tab.
3. Select Add item.
4. Specify the following details:

Indicator - Specify the entity details and define the expiration of the indicator.
Response Action - Specify the action to be taken and provide a description.
Scope - Define the scope of the machine group.

I created a seperate device group for mobile devices, but you can assign to all devices if you want to use the rules across multiple platforms. Also, I am only using bet365 and 888sport as examples. In no way I am implying that these are malicious sites.


5. Review the details in the Summary tab, then click Save.


If you are dealing with multiple entries, then you have the option to import a csv as well.

End User Experience

On an MDE onboarded mobile device, when user tries to access the urls added as part of the blocked action rules in IoC, Defender will block them and the user will see the screens similar to ones shown below.

On Android



On iOS



Connection attempts get logged on Microsoft Defender 365 portal as well. This can be monitored directly under the indicators. 



Conclusion

It is great that Microsoft have extended the IoC capability to mobile devices. It will be great if Web content filtering rules could be extended as well, but even without it, IoC is a great addition. This will allow SecOps to implement rules to allow, audit, warn, block access to URLs and IPs that the organization wants to control. Until next time..

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