How can I comprehensively validate the security and integrity of a Windows 11 Pro system against advanced or undetected threats?

Question

I am seeking guidance on how to thoroughly validate the security and integrity of my Windows 11 Pro system.

My objective is to confirm that there is no malware or unauthorized software that may have obtained elevated privileges while remaining undetected by:

• Microsoft Security
• Windows Defender Firewall

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Additionally, I would like to assess whether any dormant or low-visibility programs could exist on the system, particularly those designed for:

• Credential collection
• Data aggregation
• Other unintended or unauthorized activities

This inquiry is based on an observation I recently made:

• I found a large (167 GB) .txt file on my system Specifically in C:\Users\USER.
• The file contains:
  • Passwords
  • Security seeds phrases
  • And also other private data
  • Data associated with encrypted my wallets

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Note:

I change it completely and make new and moved to air-gapped hardware device

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Clarification:

• These data elements do exist individually on my device.
• However, I did not create or intentionally compile them into a single file of this nature.

I would like to understand whether this could result from:

• Legitimate system or application behavior, or
• Unintended data aggregation or potential misuse

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I would appreciate your guidance on the following:

• How can I reliably verify that no privilege-escalated or stealth malware is present on my system?
• What tools or methods can be used to detect dormant, hidden, or low-activity processes?
• How can I confirm that:
  • Microsoft Security and
  • Windows Defender Firewall

Are functioning correctly and have not been bypassed or altered?

Answer 1

A 167 GB plain text file aggregating passwords, seed phrases, and wallet-related data is not normal behavior for Windows or legitimate applications. The operating system does not consolidate sensitive user data into a single text file, and reputable password managers or wallet software do not export secrets in that way without explicit user action. The size alone strongly suggests either automated logging/collection over time or some form of bulk data dump. That makes it reasonable to treat the system as potentially compromised rather than assuming a benign explanation.

At this point the most reliable way to regain trust in the system is not purely inspection but re-establishing a known-good baseline. If you need high assurance, backing up only essential non-executable personal files, securely wiping the drive, and reinstalling Windows from trusted installation media is more dependable than trying to prove the absence of sophisticated malware. Anything running with elevated privileges or kernel-level access can hide from user-space tools, including Defender.

If you still want to investigate before taking that step, begin by examining the origin of the file itself. Check its creation and modification timestamps and whether any process has recently accessed it. You can use:

dir "C:\Users\USER\yourfile.txt" /T:C
dir "C:\Users\USER\yourfile.txt" /T:W

and review NTFS metadata more deeply with Sysinternals tools like streams.exe and sigcheck.exe. Also inspect file handles with Process Explorer or:

handle.exe yourfile.txt

to see if any process is interacting with it. That can sometimes reveal a data collector or logger still present.

For detecting stealth or low-visibility persistence, the most effective single tool is Sysinternals Autoruns. Run it as administrator, enable “Hide Microsoft Entries,” and carefully review everything that starts automatically, especially drivers, scheduled tasks, WMI subscriptions, and services. Pay attention to unsigned binaries, unusual paths (especially under user profile directories), and anything with random-looking names. Pair this with Process Explorer to inspect running processes, verify signatures, and check parent-child relationships.

To look for deeper persistence mechanisms that typical antivirus may miss, inspect scheduled tasks and WMI event subscriptions:

schtasks /query /fo LIST /v

and

powershell -command "Get-WmiObject -Namespace root\subscription -Class __EventFilter"

Unexpected entries there can indicate stealth persistence.

You can also use Microsoft Defender Offline Scan, which runs outside the normal OS environment and is harder for malware to evade. In addition, running a second-opinion scanner such as Microsoft Safety Scanner or a reputable offline rescue disk can help identify things Defender might miss, though no scanner guarantees detection of well-designed threats.

To verify Defender and the firewall themselves have not been tampered with, check their configuration and service state. In PowerShell:

Get-MpComputerStatus

and

Get-Service WinDefend, mpssvc

Both should be running, and real-time protection should be enabled. For firewall rules:

netsh advfirewall show allprofiles

Look for profiles being off or rules that broadly allow inbound connections. Also review:

Get-NetFirewallRule | where {$_.Enabled -eq "True"}

for anything unusual.

Event logs can provide additional clues. Review Security and System logs in Event Viewer, especially for logon events, privilege use, service installations, and unexpected scheduled task creation. Filtering for Event IDs like 4624, 4672, and 4697 can highlight suspicious activity.

Network inspection is also useful. Check active connections and listening ports:

netstat -abno

and correlate process IDs with what you see in Task Manager or Process Explorer. Unexpected outbound connections from unknown processes are a red flag.

Given the nature of the file you found, it is also important to consider that the source could have been something like a clipboard logger, keylogger, or application scraping local storage over time. Even if you remove visible traces, you cannot be fully confident the system is clean if such a mechanism existed.

The conclusion is that this is unlikely to be legitimate system behavior. If any sensitive material like wallet seeds was present on that machine, treating it as compromised was the right move, and migrating to air-gapped storage was a necessary step. For complete assurance, a clean reinstall combined with updating firmware, rotating all credentials again from a known-safe device, and avoiding reintroducing unknown executables from backups is the safest path.

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hth

Marcin