Detect Email Addresses in Sumo Logic CSE
Adversaries may gather email addresses that can be used during targeting. Even if internal instances exist, organizations may have public-facing email infrastructure and addresses for employees. Adversaries may gather email addresses from publicly accessible sources such as social media, company websites, and leaked credential databases. Additionally, adversaries may actively enumerate valid email addresses by probing authentication services — for example, querying the Microsoft GetCredentialType API endpoint or Exchange Autodiscover to determine whether a given address is a valid account in Office 365 or on-premises Exchange environments. Gathered email addresses enable spearphishing campaigns, credential brute force attacks, business email compromise, and social engineering operations.
MITRE ATT&CK
- Tactic
- Reconnaissance
- Technique
- T1589 Gather Victim Identity Information
- Sub-technique
- T1589.002 Email Addresses
- Canonical reference
- https://attack.mitre.org/techniques/T1589/002/
Sumo Detection Query
(_sourceCategory=azure/signinlogs OR _sourceCategory=azure/activedirectory OR _sourceCategory=o365/audit)
| json field=_raw "properties.status.errorCode" as errorCode nodrop
| json field=_raw "properties.userPrincipalName" as username nodrop
| json field=_raw "properties.ipAddress" as clientIP nodrop
| json field=_raw "properties.appDisplayName" as appName nodrop
| json field=_raw "properties.userAgent" as userAgent nodrop
| where errorCode in ("50034", "50053", "50055", "50056")
| where !isNull(clientIP) and clientIP != ""
| where !isNull(username) and username != ""
| timeslice 1h
| count_distinct(username) as UniqueUsernames, count as AttemptCount by clientIP, userAgent, _timeslice
| where UniqueUsernames >= 10
| eval Verdict = if(UniqueUsernames >= 50, "High Confidence Enumeration", if(UniqueUsernames >= 20, "Moderate Enumeration", "Low-Level Enumeration"))
| eval EnumerationRatePerMin = round(UniqueUsernames / 60, 2)
| sort by UniqueUsernames desc
| fields _timeslice, clientIP, userAgent, UniqueUsernames, AttemptCount, EnumerationRatePerMin, VerdictDetects email address enumeration via Azure AD sign-in failure analysis in Sumo Logic. Parses JSON payload fields from Azure AD and Office 365 sign-in log events to extract error codes, user principal names, and source IP addresses. Uses timeslice to bucket events into 1-hour windows and count_distinct to identify source IPs probing 10 or more unique account names within an hour. Applies a three-tier confidence verdict matching the reference KQL and SPL logic. Adjust _sourceCategory values to match your collector configuration.
Data Sources
Required Tables
False Positives & Tuning
- Bulk user provisioning or deprovisioning workflows executed from a management server that verify account existence for large batches of new hires, generating concentrated bursts of 50034 errors
- Third-party SaaS identity brokers or privileged access management platforms authenticating on behalf of many users from a single service account IP, producing high unique-username counts without adversarial intent
- Security awareness or phishing simulation vendors probing email address validity as part of campaign scoping, generating controlled authentication error volumes from known service IP ranges
Other platforms for T1589.002
Testing Methodology
Validate this detection against 5 adversary techniques from Atomic Red Team. Each test below lists the behaviour to exercise and the telemetry you should expect to see. Executable commands and cleanup steps are available with Pro.
- Test 1Azure AD Email Enumeration via GetCredentialType API (PowerShell)
Expected signal: Sysmon Event ID 1: PowerShell.exe process with CommandLine containing 'GetCredentialType' and 'login.microsoftonline.com'. Sysmon Event ID 3: Outbound network connections from powershell.exe to login.microsoftonline.com (TCP 443). Proxy/web filter logs: HTTP POST to login.microsoftonline.com/common/GetCredentialType with PowerShell User-Agent. DeviceNetworkEvents in MDE: InitiatingProcessFileName=powershell.exe, RemoteUrl containing GetCredentialType.
- Test 2Azure AD Email Enumeration via AADInternals Module
Expected signal: Sysmon Event ID 1: powershell.exe with CommandLine containing 'AADInternals' and 'UserEnumerationAsOutsider'. Sysmon Event ID 3: Network connections to login.microsoftonline.com and related Microsoft AAD endpoints. PowerShell ScriptBlock Log Event ID 4104 capturing the full module invocation. Windows Security Event ID 4688: Process creation for powershell.exe with command line auditing enabled. Proxy logs: HTTP requests with AADInternals User-Agent string to Microsoft authentication endpoints.
- Test 3Email Enumeration via Sign-in Attempt with Non-Existent Accounts (Generates SigninLogs 50034)
Expected signal: Azure AD SigninLogs: 10 entries with ResultType=50034 (UserAccountNotFound) for each probed address, all from the same source IP. These entries are visible in the Azure Portal under Azure AD > Sign-in logs and in Microsoft Sentinel's SigninLogs table within 5-15 minutes. Field ClientAppUsed will show 'Other clients'.
- Test 4OSINT Email Harvesting Simulation via Python Requests (LinkedIn/Web Scraping Pattern)
Expected signal: Sysmon Event ID 1: python3.exe process creation with CommandLine containing 'theHarvester' User-Agent string. Sysmon Event ID 3: Network connections from python3.exe to target hosts over TCP 443/80. DeviceNetworkEvents in MDE: InitiatingProcessFileName=python3.exe, RemoteUrl matching target sites. Proxy logs: HTTP GET requests with theHarvester User-Agent string — this User-Agent string is well-known and often blocked/alerted by web proxies.
- Test 5Exchange Autodiscover Email Validation Probe (curl)
Expected signal: Sysmon Event ID 1: curl.exe process creation with CommandLine containing 'autodiscover' and target email addresses. Sysmon Event ID 3: Outbound network connections from curl.exe to autodiscover.targetdomain.com over TCP 443. Exchange IIS Access Logs (W3SVC): POST requests to /autodiscover/autodiscover.xml with 401 response codes, source IP, and User-Agent 'curl/*'. Windows Security Event ID 4625 (Logon Failure): if Basic Authentication is attempted against Exchange.
References (9)
- https://attack.mitre.org/techniques/T1589/002/
- https://o365blog.com/post/just-looking/
- https://github.com/gremwell/o365enum
- https://grimhacker.com/2017/07/24/office365-activesync-username-enumeration/
- https://www.hackers-arise.com/email-scraping-and-maltego
- https://www.cnet.com/news/massive-breach-leaks-773-million-emails-21-million-passwords/
- https://learn.microsoft.com/en-us/azure/active-directory/reports-monitoring/concept-sign-ins
- https://github.com/dafthack/MSOLSpray
- https://github.com/0xZDH/o365spray
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