Microsoft Defender Sent a Developer’s Unreleased Programs to Microsoft: How to Check Your PC

A Default, Not a Bug

Defender did what Microsoft says it does. Microsoft’s sample submission documentation names “Send safe samples automatically” as the default on Windows, macOS and Linux. Safe samples, in Microsoft’s words, are files “considered to not commonly contain PII data. Examples include .bat, .scr, .dll, and .exe.” Only a file that’s likely to hold personal information triggers a prompt.

That rule waves through exactly the files a developer cares about most. A program you compiled this morning holds no phone numbers, so by Microsoft’s definition it’s safe to send.

Stimpson’s objection is about consent: “The absence of personal information doesn’t tell Microsoft whether I’m willing to share the program.”

Why builds, and so many of them? Defender first sends a file’s metadata to Microsoft’s cloud, which asks for the file itself when it “can’t reach a conclusive verdict”. A fresh compile is a file nobody has seen before, with no reputation behind it. That would explain one test program making up 201 of the 217 uploads, though this is our reading of Microsoft’s description, not something Stimpson states. Once a file is uploaded, Microsoft writes, it “can be scanned, detonated, and processed through big data analysis machine-learning models”.

So “safe” means safe under Microsoft’s privacy rules. Whether it’s safe for your unreleased product is a question Defender never asks.

The Setting That Switched Itself Back On

On 28 October at 17:56, Stimpson turned submission off in PowerShell with Set-MpPreference -SubmitSamplesConsent 2, Microsoft’s “Never send”. Defender logged the change as event 5007. At 19:53 a second 5007 entry recorded the reverse, from 2 back to 1.

“I don’t know what changed it back,” he writes. Nothing was uploaded in the two hours the setting was off. After it came back on, 25 more files were.

The logs that could have named the process behind the change had already rotated out. A quick scan started under his account nine seconds after the switch, and he names a click in Windows Security as one possible explanation. He doesn’t claim Microsoft flipped it on purpose.

Defender’s switch has wandered before, in the other direction. On Microsoft’s Q&A forum, Windows 11 users reported in 2022 that Windows Security kept turning automatic sample submission off by itself. Microsoft’s support specialist offered workarounds, not a cause.

What Else Left His PC

• Upload volume: Windows’ per-app data counter puts MpCmdRun.exe at 2.8 GB uploaded in 30 days, about 80% of everything the PC sent to Microsoft in that time. That’s the process’s total traffic, not the size of the submitted files, as he notes.
• Folder names: Defender’s support log held 85 entries marked “command line reported as lowfi” over four days, 78 of them with his user name and project folder names. Microsoft says file names in the metadata it collects are hashed. Stimpson couldn’t confirm whether these strings were.
• Copilot: the app, which he hadn’t opened, made 41 to 54 connections to Microsoft at each of three sign-ins. He hasn’t found what starts it.

Give it the right weight. This is one PC, and connection records show which program talked to which host, not what the encrypted traffic contained. Stimpson built the monitoring tool, promotes a paid data-removal service on the same page, and writes that “an AI agent did most of the digging” after he gave it access to the tool. None of that changes what Defender’s own event log recorded, and that part you can check on your own PC. His post includes no response from Microsoft.

Check Your Own PC

Open PowerShell as administrator.

List the files Defender has uploaded. Event 2050 means, per Microsoft’s event reference, “The antimalware platform submitted a file for sample analysis”. Stimpson suggests looking for your build paths in the results.

Get-WinEvent -FilterHashtable @{ LogName='Microsoft-Windows-Windows Defender/Operational'; Id=2050 } | Select-Object TimeCreated, Message | Format-List

See every change to the setting (event 5007):

Get-WinEvent -FilterHashtable @{ LogName='Microsoft-Windows-Windows Defender/Operational'; Id=5007 } | Where-Object Message -match 'SubmitSamplesConsent' | Select-Object TimeCreated, Message | Format-List

Check the current value:

Get-MpPreference | Select-Object SubmitSamplesConsent

Microsoft lists four values: 0 = always prompt, 1 = send safe samples automatically (the default), 2 = never send, 3 = send all samples automatically.

An empty result for event 2050 doesn’t prove nothing was sent. The log only reaches back as far as its size allows.

Turning It Off, and What You Give Up

• Windows Security: Virus & threat protection → Manage settings → Automatic sample submission → Off. Then check the value with Get-MpPreference: 0 means Defender asks before each upload, 2 means it never sends.
• PowerShell: Set-MpPreference -SubmitSamplesConsent 2 sets “Never send” directly.
• Windows Pro, Enterprise or Education: in the Group Policy editor (gpedit.msc), go to Computer Configuration → Administrative Templates → Windows Components → Microsoft Defender Antivirus → MAPS, open “Send file samples when further analysis is required”, set it to Enabled and choose “Never send”. A setting made by policy shows as managed in Windows Security, so a stray click can’t undo it.

Whichever you pick, run the event 5007 check again a few days later to see whether the value stayed where you put it.

Microsoft is open about the cost. “Never send” also switches off Block at First Sight, the feature that lets its cloud stop brand-new malware within seconds, and the cloud then judges files on metadata alone. Metadata is still sent for detections. Microsoft says both “Always prompt” and “Never send” lower the protection state of the device.

On a PC where you only run software other people wrote, that trade buys you little. On a machine where you compile your own, “Always prompt” is the sensible middle: Defender still asks for samples, and you decide which of your builds leave the house.