Microsoft Defender for Endpoint Internals 0x03 — MDE telemetry unreliability and log augmentation

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Microsoft Defender for Endpoint Internals 0x03 — MDE telemetry unreliability and log augmentation

In part one and part two of this series, we have established that Microsoft Defender for Endpoint (MDE) uses sampling and caps on events to limit the amount of telemetry being uploaded to the cloud. If you have not read these two posts, please take some time to go through them to get more context on what is described within this article.

There probably are many reasons why Microsoft has decided on this design of limiting the amount of telemetry that ends up in the portal. The primary ones I can think of are bandwidth consumption, expected usage, performance (on the cloud side) and likely the most dominant one: cost.

Since MDE is a fixed-fee solution and Microsoft has shareholders that want to get some return on their investments, this can’t be a limitless philanthropic service. Therefore, Microsoft needs to apply some mechanisms to have a predictable maximum set of telemetry per onboarded device.

One thing that we noticed when supporting our clients, is that a predominant part of them did not utilize the search and custom detection capabilities prior to getting us to support them. Assuming this applies to a large portion of the Microsoft customer base, this might also add to some of the aforementioned design decisions.

To be very clear, the sampling and caps are applied as defined in the MDE configuration, which is maintained by Microsoft. These logs are shipped to a log analytics-like workspace in your tenant, which you can partially access via the M365 Defender portal. I deliberately state ‘partially’, because not all telemetry seems to be exposed to us as users. In some cases this is because some of the components are still in preview or the data is used only for EDR detections. It can also be the case this telemetry is not deemed valuable for us, the users of this service.

Cross post from medium.com, please read the full article here:

https://medium.com/falconforce/microsoft-defender-for-endpoint-internals-0x03-mde-telemetry-unreliability-and-log-augmentation-ec6e7e5f406f