Auto-Remediating Stale Local Admin Group Membership Drift

#The Old Way vs The New Way

Under the old way, endpoint security relied on a technician manually cross-referencing a wiki-hosted spreadsheet of approved administrators against local group membership pulled from each machine during a scheduled audit window. Any account that had crept into the Administrators group following a break-glass session, a departed contractor, or an unreversed helpdesk override sat undetected until the next audit cycle, sometimes weeks later. Remediation meant a technician manually removing the account, often after an awkward email exchange asking why the access was still present. Offline endpoints were simply missed entirely, leaving gaps that nobody tracked.

The new way replaces this reactive spreadsheet exercise with a continuously enforced desired-state model. A scheduled script compares actual group membership against a version-controlled allow-list manifest every few hours, removes unauthorised accounts automatically, and fires a webhook the moment remediation occurs. Drift is corrected within a single scan cycle rather than surviving until the next manual audit, giving the security team real-time evidence instead of a monthly compliance ticket queue.

#Manifest Governance and Change Control

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Required Permissions for the RMM Deployment Account

The service account or deployment profile used to push the detection and remediation scripts must hold local execution rights on target endpoints via the RMM agent’s SYSTEM context, but must not additionally hold rights to modify the allow-list manifest repository. Separating the account that executes remediation from the account that authors policy prevents a single compromised credential from both altering the approved SID list and suppressing its own removal. Grant the manifest repository write access only to named individuals on the endpoint security team, enforced through branch protection rules requiring the second-reviewer approval described earlier. Confirm this separation by running Get-Acl against the manifest share and cross-referencing group membership against your identity provider’s role export monthly.

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Pilot Ring Configuration Detail

When configuring the 25-endpoint pilot ring, tag devices in the RMM console with a distinct label such as admin-drift-pilot rather than relying on an existing patch ring, because overlapping rings make it difficult to isolate false positives caused by the drift script from unrelated patch failures. Run the detection script in dry-run mode first by commenting out the $Group.Remove() call and observing only the write-output lines for a full seven-day cycle before enabling live removal. This surfaces role-based exceptions — for example, a build engineering laptop that legitimately requires a rotating contractor SID — that the manifest has not yet captured.

#Monitoring and Alert Thresholds

Beyond the three-strikes-in-24-hours escalation already defined, configure a secondary threshold in your SIEM to flag when more than 5% of the fleet triggers a remediation event within a single scheduled scan window. A fleet-wide spike of this size almost always indicates a manifest corruption or a bad sync rather than genuinely widespread unauthorised access, and should pause further automated removal pending manual review. Configure a dashboard tile that plots remediation event volume against manifest version number on the x-axis, which makes it straightforward to correlate a spike with a specific commit during a post-incident review.

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Distinguishing Genuine Drift from Sync Failure

A realistic failure symptom is a wave of removals immediately following a manifest push, where accounts that were approved under the previous manifest version are removed because the new version has not yet reached every endpoint. This is not malicious drift; it is a distribution race condition. Check the RMM’s file deployment status view, as referenced under manifest governance, before treating a spike as a security event. If more than 10% of endpoints report a manifest file hash that does not match the latest committed version after four hours, treat this as a distribution failure and halt the remediation schedule fleet-wide until resolved.

#Change-Control Record Template

Every standard change raised for a manifest SID addition or removal should capture, at minimum: the requesting individual, the approving reviewer, the affected device tag count, the manifest commit hash before and after, and the scheduled activation time. Store this record alongside the pull request link in your change management system rather than duplicating the justification text, since divergence between the two creates ambiguity during audit. For normal changes touching script logic, additionally record the rollback script version and confirm a tested restore point on at least one pilot endpoint before the change window opens.

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Sample Change Record Fields

#Common Failure Symptoms and Their Causes

• Detection script runs but produces an empty log file repeatedly across multiple endpoints — check that the scheduled task or RMM job has read access to the manifest path, as a permissions regression will cause the script to fail silently on the Get-Content call rather than throwing a visible error.
• Webhook payloads arrive with a null device field — this typically indicates the $env:COMPUTERNAME environment variable is not resolving under the execution context used by certain RMM agents; test by echoing the variable in an ad hoc script run first.
• Remediation removes an account, then re-adds it on the next cycle, then removes it again — this loop indicates two conflicting manifest versions are being served to the same device group, usually from a stale CDN cache or a duplicate deployment policy targeting the same OU.
• Legitimate break-glass account removed mid-incident — confirm the break-glass SID is present in the manifest’s exception list with no expiry date, and if it must be temporary, ensure the expiry is set generously enough to outlast the incident response window.

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Escalation Path Beyond the Technician Tier

If fleet-wide remediation must be paused per the 5% threshold above, the decision to resume sits with the endpoint security team lead, not the on-call technician, because resuming prematurely against an uncorrected manifest can trigger a second wave of incorrect removals. Document the pause and resume timestamps in the same change record used for the original manifest update, and attach the corrected manifest commit hash to close the loop.

#Safe Rollback Beyond Individual Account Restoration

If a defective script version has already propagated fleet-wide, the safest rollback is to disable the scheduled task or RMM policy entirely — rather than attempting to push a corrected script under time pressure — pending a full pilot-ring retest of the fix. Re-enable only after the corrected version has completed one clean scan cycle across the pilot ring with zero unintended removals logged.

The allow-list manifest must not be treated as a static artefact. Every amendment requires a pull request against the manifest repository, reviewed by at least one member of the endpoint security team who is not the requester, before merge. The pull request description must record the business justification (contractor onboarding, role change, break-glass grant), the device tags affected, and an expiry date if the grant is temporary. On merge, tag the commit with a semantic version and record that version in your change management system as a standard change, not a normal change, provided the diff only adds or removes SIDs and does not alter script logic. Any modification to the detection or remediation script itself — for example, altering the removal exclusion for the built-in Administrator account — must go through a normal change with a rollback plan attached, because a defective exclusion list could strip legitimate break-glass access fleet-wide within a single scan cycle.

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Manifest Distribution Verification

Before assuming a manifest update has propagated, confirm distribution through your RMM’s file deployment status view rather than trusting the push job’s

The old way of policing local administrator group membership involved a technician exporting a spreadsheet of “approved admins” from a wiki, running a scheduled scan against endpoints, and manually removing accounts that had crept into the Administrators group after a break-glass session, a contractor departure, or a helpdesk override that never got walked back. This produced a monthly compliance ticket queue full of manual net localgroup removals and awkward emails asking “why are you still a local admin on this laptop?” It is reactive, slow, and it always misses machines that were offline during the audit window.

The new way treats local admin membership as a desired-state configuration, continuously reconciled by a scheduled script and a webhook-triggered alert, so drift is corrected before a compliance auditor or attacker ever finds it.

#Prerequisites and Permissions

• Deployment via RMM or Intune Proactive Remediation with SYSTEM-level script execution rights.
• An authoritative allow-list (security group or signed JSON manifest) defining approved local admin accounts per device role.
• Least privilege: the remediation script needs local Administrators group read/write only; it must not run under a domain admin credential.
• Test scope: pilot ring of no more than 25 non-production endpoints before fleet-wide rollout.

#Implementation Steps

1. Define the allow-list. Action: publish a JSON manifest of approved SIDs per device tag. Expected result: a version-controlled source of truth. Evidence: commit hash in your repo.
2. Deploy the detection script on a schedule (every 4 hours). Action: enumerate Administrators group membership and diff against the manifest. Expected result: a structured drift report. Evidence: exported CSV or log entry per run.
3. Deploy the remediation script to auto-remove unauthorised members. Action: execute removal only for accounts not present in the allow-list. Expected result: group membership reset to baseline. Evidence: before/after membership snapshot in the RMM console.
4. Fire a webhook to your SIEM or Teams channel on every remediation event. Action: POST a JSON payload describing device, account removed, and timestamp. Expected result: real-time visibility without a ticket being raised. Evidence: webhook delivery log with 200 response.
5. Schedule a weekly summary report for the security team. Action: aggregate drift events. Expected result: trend data proving deflection. Evidence: report attached to compliance tracker.

#Detection and Remediation Script (PowerShell)

1$AllowList = Get-Content -Raw -Path "C:\ProgramData\OpsPlaybook\admin-allowlist.json" | ConvertFrom-Json
2$Group = [ADSI]"WinNT://./Administrators,group"
3$Members = @($Group.Invoke("Members")) | ForEach-Object {
4  $_.GetType().InvokeMember("Name", 'GetProperty', $null, $_, $null)
5}
6
7foreach ($member in $Members) {
8  if ($AllowList.ApprovedAccounts -notcontains $member -and $member -ne "Administrator") {
9    Write-Output "Removing unauthorised admin: $member"
10    $Group.Remove("WinNT://./$member,user")
11
12    $payload = @{
13      device    = $env:COMPUTERNAME
14      account   = $member
15      action    = "removed"
16      timestamp = (Get-Date).ToString("o")
17    } | ConvertTo-Json
18
19    Invoke-RestMethod -Uri "https://ops-webhook.internal.kby.io/admin-drift" -Method Post -Body $payload -ContentType "application/json"
20  }
21}

Expected output example: Removing unauthorised admin: contractor_jsmith followed by a 200 response logged in the webhook receiver.

#Verification and Expected Evidence

#Rollback

If an approved account is mistakenly removed (for example, a manifest sync lag), re-add via $Group.Add("WinNT://./accountname,user") executed by a technician with local admin rights, then correct the manifest before the next scheduled run to prevent re-removal loops.

#Failure and Escalation Conditions

• Wake a human technician if the same device triggers three or more remediation events within 24 hours — this indicates a persistent unauthorised elevation source, not benign drift.
• Escalate if the webhook receiver returns non-200 responses for more than two consecutive cycles, as this breaks audit visibility.
• Blast radius: limit script execution to Tier-1 workstation OU; server OUs require separate change control.

#Measuring Ticket Deflection

Track monthly count of manual “who is a local admin” audit tickets before and after rollout, alongside the count of auto-remediated drift events. A successful deployment should show audit-related tickets falling toward zero within two reporting cycles while the webhook log demonstrates continuous, silent enforcement.

Further reading: see Microsoft’s guidance on managing local accounts and group membership and Microsoft Intune’s proactive remediation script documentation for scheduling detection and remediation pairs at scale.

Local admin drift is one of the quietest compliance risks in any fleet because it accumulates silently between audits. By converting the audit-and-remove cycle into a continuously enforced desired-state script with webhook-driven visibility, the ticket queue for “unauthorised admin access” simply stops generating new entries, and the security team gets real-time evidence instead of a monthly spreadsheet.