Exactly. But I'd add a critical, often overlooked detail buried in the documentation: you can technically *disable* the local AV's real-time protection and still feed sensor data to MDE's "brain."
It's a dumb thing to do, but it reveals the architecture. The EDR platform is consuming a *stream* of raw OS events (file creations, process forks, registry changes) from that sensor, not just AV scan results. The "blocking" is separate from the "seeing."
This is why you can replace the AV engine with a third-party one (like in passive mode) and MDE keeps working - it's just sipping from a different telemetry firehose. The cost implication is that this stream is what drives those Log Analytics ingestion charges everyone's sweating.
Exactly. That "feel smarter" detection is the behavioral analysis in the cloud, but it introduces a new failure mode: latency.
You can have a perfect sensor feed and a brilliant cloud brain, but if the network link is saturated or the cloud service is throttling your ingestion, you get delayed detection. The local AV component blocks a known hash in milliseconds. MDE's fancy correlation might take minutes to piece the story together and push a verdict back down.
For ransomware, those minutes matter. That's why the architecture still needs a capable local component for instant blocking, not just as a dumb telemetry feed.
Build once, deploy everywhere
That latency point is super real. So if the cloud is down or slow, does the local component ever do its own blocking based just on what it knows? Or is it totally reliant on the cloud verdict before it can act?
Totally. That "different telemetry firehose" detail is key for anyone budgeting the platform shift. People think they're just replacing an AV license, but the real cost is ingesting all that raw event data for the cloud brain to analyze.
It also changes the security model. A third-party AV in passive mode might miss a novel local threat, but MDE's cloud side could still spot the correlated activity across other machines later. You're trading some immediate, endpoint-specific protection for that broader, delayed insight.
Cheers, Henry
>Does the Antivirus component actually get *better* at its job when it's feeding data into MDE?
Yeah, it does. The cloud side gives the local component a real-time update.
Think of the basic AV as a bouncer with a static list of known troublemakers. The MDE-connected version is that same bouncer, but now he's getting a radio alert from the security office saying, "Heads up, we just saw a guy in a red hat try the back door of three other clubs on this street." So he can stop that specific behavior locally, not just a known bad file.
It's the same core engine, but its intelligence is supercharged by the wider view.
data over opinions
Exactly! That supercharged intelligence is the real game changer and what justifies the whole platform shift. The local engine gets what I'd call "community updates" from the cloud brain.
But there's a subtle catch I've noticed in my own testing: that cloud-fed intelligence isn't always about a *specific* bad file. It can be about a *sequence*. Like, the bouncer might not know the guy in the red hat is bad, but he now knows to stop anyone who tries to open the emergency exit, then immediately touch the safe. The local AV blocking the second action because the cloud flagged that behavioral chain across the tenant.
That's where the magic is, but also where you can get false positives if the chain isn't tuned right for your environment.
Solid breakdown. That architectural shift hits home when you're knee-deep in logs at 3 AM.
You mention MDE correlating "dozens of other sensors" - this is the part that people gloss over. That sensor data from Intune, Azure AD, and even Defender for Cloud becomes part of that single attack story. A single weird login attempt from a new country might get a shrug from AV, but when MDE sees that same identity spawned a suspicious process on a server an hour later, that's the "nervous system" in action.
The flip side is, of course, alert fatigue. Now you're not just vetting AV alerts, you're triaging these cross-domain stories, some of which are just... weird admin behavior. Gets noisy fast if you don't tune it.
NightOps
You've nailed the operational reality. The "nervous system" analogy is perfect, but the alert fatigue from it is its own specialty. Tuning this isn't like tweaking an AV exclusion list. You're now defining what constitutes a "normal" story across identity, endpoint, and cloud, which requires a much broader context than most security teams initially have.
The real administrative burden comes when you need to suppress "weird admin behavior" alerts without creating a blind spot. You're not just allowing a file hash, you're effectively telling the system that a specific sequence of events, say, a PowerShell execution from that admin's account after an irregular login, is acceptable. That's a far more powerful, and potentially dangerous, allow rule than most are used to creating.
- Mike