Azure CLI Password Sprays Are Exploding – Here’s How To Detect, Block, And Investigate Them + Video

Introduction:

Microsoft Entra ID (formerly Azure AD) is under siege. Over the past several months, security professionals across the globe have reported a sharp increase in password spray attacks specifically targeting Azure CLI authentication endpoints. Unlike traditional brute-force attacks that hammer a single account with thousands of passwords, password spraying uses a handful of common passwords across thousands of accounts – a quieter, more evasive approach that often flies under the radar. What makes the current wave particularly concerning is the use of Azure CLI as the attack vector, with user-agents like “Python” and automated tooling that systematically tests credentials against Entra ID tenants. This article breaks down the technical mechanics of these attacks, provides actionable detection strategies using Microsoft Defender for Cloud Apps and Sentinel, and delivers a comprehensive defense-in-depth guide to harden your Entra ID environment.

Learning Objectives:

Understand the anatomy of Azure CLI-targeted password spray attacks and the tools adversaries use
Configure Microsoft Defender for Cloud Apps activity policies to detect suspicious user agents
Implement Conditional Access policies, Smart Lockout, and Entra ID Protection to block attacks pre-authentication
Build KQL hunting queries in Microsoft Sentinel to proactively identify password spray patterns
Execute incident response playbooks for confirmed password spray compromises

The Attack Surface: Why Azure CLI Is the New Favorite Vector

Azure CLI is a cross-platform command-line tool for managing Azure resources. While legitimate administrators use it for automation and infrastructure-as-code workflows, attackers have discovered that it provides an ideal authentication endpoint for password spraying. The “Microsoft Azure CLI” client application appears in Entra ID sign-in logs, and because it supports various authentication flows – including resource owner password credentials (ROPC) and device code flow – it can be targeted without triggering the same level of scrutiny as browser-based logins.

Common Attack Tools:

MSOLSpray – The original password spraying tool for Microsoft Online accounts
Entraspray – A Python rewrite of MSOLSpray with enhanced features including random user-agent selection and FireProx support for IP rotation
AzureRedOps – A comprehensive offensive security toolkit that wraps authentication, token management, and password spraying behind a consistent CLI
Spray365 – Features customizable execution plans designed to bypass Azure Smart Lockout

The telltale signs in your sign-in logs include the `Microsoft Azure CLI` application name, non-standard user agents (often “Python” or custom strings), and authentication attempts originating from unusual geolocations.

Detection: Microsoft Defender for Cloud Apps “Suspicious User Agents” Policy

As noted by Dan Parton, the Defender for Cloud Apps policy “Activities from suspicious user agents” is actively picking up these attacks and generating alerts. This policy is a critical first line of defense for identifying Azure CLI password spray attempts.

Step‑by‑Step: Create a Suspicious User Agent Activity Policy

Navigate to the Microsoft Defender Portal → Cloud Apps → Policies → Policy management

2. Select Create policy → Activity policy

3. Under Activity filters, configure:

User agent tag → equals → `Outdated browser` and `Outdated operating system`
– Alternatively, create a custom filter for User agent → contains → `Python` or `azure-cli` (to catch non-standard clients)

Set the Alert severity to Medium or High
Under Governance actions, configure automated responses such as:

– Suspend user (if multiple violations)
– Require MFA re-authentication
– Notify security team via email or SIEM integration

Best Practice: Before creating this policy, configure IP address ranges in Defender for Cloud Apps to whitelist trusted office/VPN IPs. This helps the machine learning models accurately classify known locations and reduces false positives.

Pre-Authentication Defense: Smart Lockout and Entra ID Protection

Password spray attacks succeed when attackers can make unlimited failed authentication attempts without consequence. Microsoft Entra ID Smart Lockout is enabled by default and provides an intelligent defense.

Smart Lockout Default Settings:

Lockout threshold: 10 failed attempts
Lockout duration: 1 minute (increases with repeated attacks)

What Makes It “Smart”? Smart Lockout maintains two separate counters – one for familiar locations (IPs where users have successfully logged in before) and one for unfamiliar locations. An attacker in an unfamiliar location gets locked out after 10 attempts, while legitimate users logging in from trusted IPs remain unaffected.

To Customize Smart Lockout:

Navigate to Microsoft Entra admin center → Protection → Authentication methods → Password protection

2. Under Custom smart lockout, set:

Lockout threshold: 5–10 (lower for high-risk tenants)
Lockout duration in seconds: 60–300

Entra ID Protection Risk Policies:

Enable sign-in risk and user risk policies to automatically block or challenge risky authentications:
1. Go to Entra ID → Security → Identity Protection
2. Create a Sign-in risk policy – configure to Block access when risk level is Medium or High
3. Create a User risk policy – configure to Require password change when user risk is High

Identity Protection detects password spray attacks as a native risk detection, leveraging signals including anonymous IP usage, leaked credentials, and unusual authentication patterns.

4. Conditional Access: Blocking Azure CLI Authentication

Conditional Access policies provide granular control over which clients and authentication flows can access your tenant. For Azure CLI password spray mitigation, two policy types are essential:

Policy A: Block Legacy Authentication

Microsoft’s analysis shows that more than 99% of password spray attacks use legacy authentication protocols. Blocking legacy authentication eliminates the majority of spray vectors.

Navigate to Entra ID → Protection → Conditional Access → Policies

2. Select New policy

3. Assignments → Users → All users

Cloud apps or actions → All cloud apps

5. Conditions → Client apps → Configure:

Exchange ActiveSync clients → Yes
Other clients → Yes (this captures Azure CLI, PowerShell, and other non-browser clients)

6. Grant → Block access

7. Set to Report-only initially to assess impact

Policy B: Block Azure CLI for Specific Users or All Users

To specifically target Azure CLI authentication:

Target resource → Azure Resource Manager (the modern equivalent of “Windows Azure Service Management API”)
Conditions → Client apps → Other clients → Yes

3. Grant → Block access

Important Caveat: When targeting “All resources” or “All cloud apps,” Azure CLI sign-in flows involve multiple dependent resources (Azure Resource Manager, Graph endpoints), which can cause unexpected policy evaluation behavior. Test thoroughly in Report-only mode.

Policy C: Location-Based Blocking

If your organization operates in specific regions, create Named Locations and block sign-ins from high-risk countries.

Hunting with KQL: Building Password Spray Detection Queries in Microsoft Sentinel

Microsoft Sentinel includes built-in analytic rules for password spray detection, but custom KQL queries enable proactive hunting and faster incident identification.

KQL Query – Detect Password Spray by IP Address:

SigninLogs
| where TimeGenerated > ago(24h)
| where AppDisplayName == "Microsoft Azure CLI"
| where ResultType !in ("0", "50125", "50126") // Exclude successful and MFA-interrupt
| summarize FailedAttempts = count(), 
UniqueUsers = dcount(UserPrincipalName),
UserList = make_set(UserPrincipalName) 
by IPAddress, ClientAppUsed, UserAgent
| where FailedAttempts > 10 and UniqueUsers > 5
| project IPAddress, FailedAttempts, UniqueUsers, UserList, UserAgent
| order by FailedAttempts desc

Key Error Codes to Monitor:

50053 – Account locked out (Smart Lockout triggered)
50055 – Password expired
50126 – Invalid username or password

KQL Query – Identify Successful Sprays (Compromised Accounts):

SigninLogs
| where TimeGenerated > ago(24h)
| where AppDisplayName == "Microsoft Azure CLI"
| where ResultType == "0" // Successful sign-in
| where IPAddress in (
SigninLogs
| where TimeGenerated > ago(24h)
| where ResultType !in ("0", "50125", "50126")
| summarize FailedAttempts = count() by IPAddress
| where FailedAttempts > 20
| project IPAddress
)
| project TimeGenerated, UserPrincipalName, IPAddress, UserAgent, 
Location, ConditionalAccessStatus

Proactive Hunting: Create a workbook in Microsoft Sentinel to visualize failed authentication attempts by IP, user agent, and geography. Set up automation rules to automatically add malicious IPs to Named Locations when thresholds are exceeded.

6. Incident Response: When a Password Spray Succeeds

Despite best efforts, some spray attempts may succeed. Follow this response playbook:

1. Immediate Containment:

Revoke all active sessions for affected users (Revoke-AzureADUserAllRefreshToken or portal)
Reset passwords immediately – require strong, unique passwords
Block Azure CLI access for affected users via Conditional Access

2. Investigation:

Review Entra ID sign-in logs for the affected user – identify the specific CLI application, source IP, ASN, and authentication timing
Check for Risky Sign-ins in Entra ID Protection
Investigate whether the compromised account performed any resource modifications, data exfiltration, or privilege escalation

3. AD FS Logging (if hybrid):

Set auditing to Verbose using PowerShell:
```
Set-AdfsProperties -AuditLevel Verbose
```
Send AD FS logs to SIEM for correlation

4. Post-Incident Hardening:

Enforce MFA for all users (Microsoft will enforce MFA broadly in 2026)
Implement authentication strengths – require Passwordless MFA for privileged roles
Regularly review and update Named Locations and Conditional Access policies

What Undercode Say:

Password spray attacks targeting Azure CLI are not hypothetical – they are happening now, at scale, across thousands of tenants worldwide. Security practitioners from Microsoft MVPs to SOC leads have confirmed a sustained increase over the past 3–6 months.
Defense requires a layered approach. No single control stops these attacks. Smart Lockout reduces velocity, Conditional Access blocks the vector, Defender for Cloud Apps detects the pattern, and Sentinel hunts for the signal. Organizations relying on MFA alone are still vulnerable – attackers have demonstrated the ability to bypass MFA through token reuse and device code phishing.
Visibility is your strongest weapon. The Entra ID sign-in logs contain the forensic evidence needed to identify, investigate, and respond to these attacks. Enable verbose logging, integrate with Sentinel, and build custom hunting queries tailored to your environment’s baseline.
Attackers are evolving. Tools like AzureRedOps and Entraspray now include features specifically designed to bypass Smart Lockout and Conditional Access policies. Defenders must continuously update their detection logic and assume that sophisticated adversaries will test their controls.
The cost of inaction is high. Compromised identities lead to data breaches, ransomware deployments, and regulatory fines. The technical controls described in this article require minimal investment (many are included in Entra ID P1/P2 licenses) and deliver immediate risk reduction.

Prediction:

+1 Microsoft’s mandatory MFA enforcement in 2026 will significantly reduce password spray success rates, but attackers will pivot to token theft, device code phishing, and OAuth consent phishing as primary vectors.
+1 AI-driven detection models in Entra ID Protection and Defender for Cloud Apps will improve false-positive rates, enabling fully automated blocking of spray attempts without human intervention.
-1 The commoditization of password spray toolkits (Entraspray, Spray365, AzureRedOps) means that even low-skill attackers can execute large-scale campaigns, increasing the volume of attacks across all tenant sizes.
-1 Organizations without Entra ID P1/P2 licenses will remain disproportionately vulnerable, as they lack Conditional Access, Identity Protection, and advanced UEBA capabilities – creating a two-tier security landscape.
+1 The security community’s collective visibility (as demonstrated by the LinkedIn thread) is accelerating threat intelligence sharing, enabling faster detection rule updates and more effective defensive countermeasures.

▶️ Related Video (78% Match):

https://www.youtube.com/watch?v=0-eLwwLxodE

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