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How to Audit Your SaaS Apps for the Malicious OAuth Backdoor That Bypasses MFA (PowerShell & KQL Scripts Included)

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Audit Your SaaS for the Malicious OAuth Backdoor that Bypasses MFA(PowerShell & KQL Scripts Included)

By CyberDudeBivash · Cloud IR & AppSec · Apps & Services · Threat Analysis · News · Crypto Security

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TL;DR 

  • Problem: OAuth “consent” grants long-lived tokens to apps that can read mail, files, CRM data without triggering MFA—perfect for stealth data theft.
  • Solution: Run a Find → Validate → Revoke → Remediate audit across Microsoft 365, Salesforce, and Google Workspace.
  • Included: Safe PowerShell and KQL snippets to enumerate risky apps, detect suspicious consents, and kick off revocation workflows.
  • Outcome: 24-hour containment; 7-day hardening plan; 30-day governance program to prevent re-consent and shadow integrations.

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Disclosure: We may earn a commission from partner links. Recommended by CyberDudeBivash for professional teams.Table of Contents

  1. Threat Model: Why OAuth Bypasses MFA
  2. Audit Prereqs & Role Setup
  3. Microsoft 365: OAuth Audit (GUI + PowerShell)
  4. Salesforce: Connected App Audit
  5. Google Workspace: Third-party App Audit
  6. KQL Detections: Consent, SPN Sign-ins, Exfil Patterns
  7. Revocation & Containment
  8. Remediation & Governance (Admin Consent Workflow)
  9. Automation & SOAR Tasks
  10. Comms, Legal, and Evidence Handling
  11. FAQ

Threat Model: Why OAuth Bypasses MFA

OAuth trades passwords for tokens. Once an employee clicks “Consent,” a third-party app gets access tokens and refresh tokens which can be renewed silently for months. Because the app talks directly to APIs (Graph, Gmail, Salesforce REST), there’s no interactive sign-in—so MFA never fires. That’s why consent phishing is the preferred route for data theft across mail, files, calendars, and CRM records.

  • Stealth: Tokens operate in the background; users don’t see prompts.
  • Scope creep: Apps often request broad scopes (Files.Read.All, Mail.Read, api/full in Salesforce, https://www.googleapis.com/auth/drive in Google).
  • Shadow IT UX: A “productivity helper” or “AI summarizer” can mask exfiltration intent.

Defender’s Intention: All scripts below are defensive, to help you audit and secure your own environment.

Audit Prereqs & Role Setup

  • Microsoft 365 (Entra ID/Azure AD): Directory Reader + Cloud App Admin (or least-privileged equivalents) to enumerate enterprise apps and consents.
  • Salesforce: System Admin or a custom read-only profile with View Setup and Configuration + App Manager access.
  • Google Workspace: Super Admin or Admin with delegated access to OAuth app controls.
  • SIEM: Microsoft Sentinel/Defender, Splunk, or equivalent with audit/sign-in logs flowing.

Use a jump box for admin actions, store secrets in a vault, and capture logs to a write-once bucket for evidence.

Microsoft 365: OAuth Audit (GUI + PowerShell)

GUI Quick Audit

  1. Go to Entra ID → Enterprise applications. Switch to All applications.
  2. Add columns: Publisher verification, Permissions, User consent, Sign-in audience.
  3. Filter for Unverified publishers, high-risk scopes (Mail.Read*, Files.Read*.All, offline_access, User.Read.All), and recently added apps.
  4. Open each app → Permissions → capture consented users/groups and scope list.

PowerShell (Conceptual, Defense-Only)

# Install-Module Microsoft.Graph -Scope CurrentUser
# Connect-MgGraph -Scopes "Application.Read.All,Directory.Read.All,AuditLog.Read.All"
# Enumerate Enterprise Apps (Service Principals)
$apps = Invoke-MgGraphRequest -Method GET -Uri "https://graph.microsoft.com/v1.0/servicePrincipals?$select=id,appId,displayName,signInAudience,appOwnerOrganizationId,verifiedPublisher&$top=999"
# Pull OAuth permissions (app role assignments & delegated scopes) for each app
# NOTE: Use least privilege; store tokens securely; log outputs for evidence.
# Flag suspicious: unverified publishers OR risky scopes OR recent creation dates.

Scopes to Flag

  • Mail.Read, Mail.ReadWrite, Mail.Send
  • Files.Read.All, Files.ReadWrite.All, Sites.Read.All
  • User.Read.All, Directory.Read.All, offline_access

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Salesforce: Connected App Audit

  1. Navigate: Setup → App Manager → Connected Apps. Export list.
  2. Review OAuth policies: Permitted Users, IP Relaxation, Refresh Token Policy, High Assurance.
  3. Flag scopes like full, api, refresh_token, and “perform requests on your behalf at any time.”
  4. Map who uses the app (Profiles/Perm Sets). Validate business owners.

Google Workspace: Third-party App Audit

  1. Admin console → Security → Access and data control → API controls → App access control.
  2. Switch to “Only allow trusted apps” if feasible; otherwise maintain a tight allowlist.
  3. Review OAuth scopes of risky apps: Gmail/Drive full access, offline access, domain-wide delegation.

KQL Detections: Consent, SPN Sign-ins, Exfil Patterns

Run in Microsoft Sentinel/Defender for Cloud Apps/Entra logs. Adjust table names per your workspace.

1) New High-Risk Consent Spike (24h)

AuditLogs
| where TimeGenerated > ago(24h)
| where OperationName has "Consent to application"
| extend Scopes = tostring(TargetResources[0].modifiedProperties[?].newValue)
| where Scopes has_any ("Mail.Read","Files.Read.All","Files.ReadWrite.All","offline_access","User.Read.All","Sites.Read.All")
| summarize count(), Apps=make_set(TargetResources[0].displayName) by InitiatedBy.user.userPrincipalName

2) Service Principal Sign-ins from Rare Geos/ASNs

SigninLogs
| where AppId != "" and ServicePrincipalId != ""
| summarize GeoCount=dcount(LocationDetails.countryOrRegion) by ServicePrincipalId
| where GeoCount > 1
| project TimeGenerated, ServicePrincipalId, GeoCount

3) Post-Consent Heavy Graph Reads

IdentityInfo
| where TimeGenerated > ago(48h)
// join with Graph activity if exported; else approximate with MailItemsAccessed/FileAccess logs
// Idea: correlate consent time → sudden surge in file/mail access by the same app/service principal

Master KQL & Azure IR (guided courses) →

Revocation & Containment

Microsoft 365

  • Remove user/admin consent for the app (Enterprise applications → Permissions).
  • Block sign-ins for the service principal or delete if unused.
  • Revoke refresh tokens for impacted users/app; reset app secrets/certs.
  • Conditional Access: temporary policy to block app ID or require compliant device.

Salesforce

  • Freeze/Block Connected App; revoke sessions; tighten IP/High Assurance requirements.
  • Rotate integration user creds; audit data export logs for blast radius.

Google Workspace

  • Block the app via App access control; remove domain-wide delegation if present.
  • Force token revocation for affected users; alert on re-consent attempts.

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Remediation & Governance 

  • Disable end-user consent. Enable Admin consent workflow in Entra ID with a strict SLA.
  • Verified publishers only: enforce verified publishers and least-privileged scopes.
  • MCAS/Defender App Governance: discover risky OAuth apps, auto-alert on anomalous access.
  • Consent reviews: monthly owner attestation; auto-expire stale consents.
  • Salesforce policies: High Assurance for privileged apps; aggressive refresh token expiry.
  • Google Workspace: “Trusted apps only” where possible; maintain a curated allowlist.

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Automation & SOAR Tasks

  • Ticket on consent event: populate app name, publisher, scopes, consentor, creation date, sign-in audience.
  • Owner validation form auto-sent; escalate if no response in 4h.
  • Conditional path: if “unknown/malicious” → revoke sessions & consent; if “business-critical” → limit scopes and enforce verified publisher.
  • Weekly attestation task to app owners; auto-disable non-responsive apps.

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Comms, Legal, and Evidence Handling

  • Evidence capture: Export app metadata, scope lists, consent records, and API access logs. Hash and timestamp.
  • Regulated data? Engage privacy/legal early; prepare notification templates and regulator timelines.
  • Internal brief: neutral one-pager (what/when/who/impact/actions/next steps). Avoid speculation.

Need Expert Help? Engage CyberDudeBivash IR & App Governance Team

  • Emergency OAuth Breach Response (M365 / Salesforce / Google)
  • Admin Consent Workflow Rollout & App Governance
  • SIEM/KQL Detections & SOAR Playbooks
  • Board-level Reporting & Tabletop Workshops

Explore Apps & Services  |  cyberdudebivash.com · cyberbivash.blogspot.com · cyberdudebivash-news.blogspot.com · cryptobivash.code.blog

Next Reads from CyberDudeBivash

FAQ

Do your scripts disable anything automatically?

No. The snippets here are defensive and read-only by default to help you audit safely. Always review and test before any change.

Is disabling end-user consent too strict?

Pair an admin consent workflow with a fast SLA. You’ll cut risky consents without choking productivity.

What’s the fastest way to contain?

Revoke app consents, block the service principal/connected app, revoke refresh tokens, and apply a temporary Conditional Access block.

CyberDudeBivash — Global Cybersecurity Brand · cyberdudebivash.com · cyberbivash.blogspot.com · cyberdudebivash-news.blogspot.com · cryptobivash.code.blog

Author: CyberDudeBivash · Powered by CyberDudeBivash · © All Rights Reserved.

 #CyberDudeBivash #OAuth #ConsentPhishing #Microsoft365 #Salesforce #GoogleWorkspace #KQL #IncidentResponse #AppSec #CloudSecurity

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